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Can time-lapse parameters predict embryo ploidy? A systematic review

  • Arnaud Reignier
    Affiliations
    Service de Médecine et Biologie du Développement et de la Reproduction, CHU de Nantes, 38 boulevard Jean Monnet, Nantes, France

    Centre de Recherche en Transplantation et Immunologie UMR 1064, INSERM, Université de Nantes, Nantes, France

    Faculté de Médecine, Université de Nantes, Nantes, France
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  • Jenna Lammers
    Affiliations
    Service de Médecine et Biologie du Développement et de la Reproduction, CHU de Nantes, 38 boulevard Jean Monnet, Nantes, France

    Centre de Recherche en Transplantation et Immunologie UMR 1064, INSERM, Université de Nantes, Nantes, France
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  • Paul Barriere
    Affiliations
    Service de Médecine et Biologie du Développement et de la Reproduction, CHU de Nantes, 38 boulevard Jean Monnet, Nantes, France

    Centre de Recherche en Transplantation et Immunologie UMR 1064, INSERM, Université de Nantes, Nantes, France

    Faculté de Médecine, Université de Nantes, Nantes, France
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  • Thomas Freour
    Correspondence
    Corresponding author.
    Affiliations
    Service de Médecine et Biologie du Développement et de la Reproduction, CHU de Nantes, 38 boulevard Jean Monnet, Nantes, France

    Centre de Recherche en Transplantation et Immunologie UMR 1064, INSERM, Université de Nantes, Nantes, France

    Faculté de Médecine, Université de Nantes, Nantes, France
    Search for articles by this author
Published:February 01, 2018DOI:https://doi.org/10.1016/j.rbmo.2018.01.001

      Abstract

      Embryo morphology assessment performs relatively poorly in predicting implantation. Embryo aneuploidy screening (PGS) has recently improved, but its clinical value is still debated, and the development of a cheap non-invasive method for the assessment of embryo ploidy status is a highly desirable goal. The growing implementation of time-lapse devices led some teams to test the effectiveness of morphokinetic parameters as predictors of embryo ploidy, with conflicting results. The aim of this study was to conduct a comprehensive review of the literature on the predictive value of morphokinetic parameters for embryo ploidy status. A systematic search on PubMed was conducted using the following key words: time-lapse, morphokinetic, aneuploidy, IVF, preimplantation genetic screening, PGS, chromosomal status. A total of 13 studies were included in the analysis. They were heterogeneous in design, patients, day of embryo biopsy, statistical approach and outcome measures. No single or combined morphokinetic parameter was consistently identified as predictive of embryo ploidy status. In conclusion, the available studies are too heterogeneous for firm conclusions to be drawn on the predictive value of time-lapse analysis for embryo aneuploidy screening. Hence, morphokinetic parameters should not be used yet as a surrogate for PGS to determine embryo ploidy in vitro.

      Keywords

      Introduction

      The ultimate objective of assisted reproduction techniques is to offer patients the highest healthy live birth rate and the lowest multiple pregnancy rate. Morphology is the most common method used for evaluating embryo quality in vitro; however, it performs poorly in identifying the embryo with the highest implantation potential, even at the blastocyst stage (
      • Gardner D.K.
      • Meseguer M.
      • Rubio C.
      • Treff N.R.
      Diagnosis of human preimplantation embryo viability.
      ). This prevents many IVF teams implementing a largely single embryo transfer policy (
      • Kushnir V.A.
      • Barad D.H.
      • Albertini D.F.
      • Darmon S.K.
      • Gleicher N.
      Systematic review of worldwide trends in assisted reproductive technology 2004–2013.
      ). Embryo morphology assessment has little predictive power for implantation because of its weak association with embryo ploidy status, which is the most critical factor for sustained implantation in IVF (
      • Gardner D.K.
      • Meseguer M.
      • Rubio C.
      • Treff N.R.
      Diagnosis of human preimplantation embryo viability.
      ). Embryo aneuploidy screening, also known as preimplantation genetic screening (PGS), allows the identification of embryo chromosomal status. Several technical improvements over the past decade have led to the identification of trophectoderm biopsy and array comparative genetic hybridization (aCGH) or next-generation sequencing as the technique of choice for PGS (
      • Gardner D.K.
      • Meseguer M.
      • Rubio C.
      • Treff N.R.
      Diagnosis of human preimplantation embryo viability.
      ). Although shown to be efficient and clinically relevant in some studies, this technique suffers from some limitations. Indeed, it raises regulatory issues in some countries (
      • Harper J.
      • Geraedts J.
      • Borry P.
      • Cornel M.C.
      • Dondorp W.J.
      • Gianaroli L.
      • Harton G.
      • Milachich T.
      • Kääriäinen H.
      • Liebaers I.
      • Morris M.
      • Sequeiros J.
      • Sermon K.
      • Shenfield F.
      • Skirton H.
      • Soini S.
      • Spits C.
      • Veiga A.
      • Vermeesch J.R.
      • Viville S.
      • de Wert G.
      • Macek Jr., M.
      ESHGESHREEuroGentest2
      Current issues in medically assisted reproduction and genetics in Europe: research, clinical practice, ethics, legal issues and policy.
      ), it can be considered invasive, it requires specific technical skills, it can take up to 24 h before obtaining the result according to the technique, and it still remains expensive (
      • Gardner D.K.
      • Meseguer M.
      • Rubio C.
      • Treff N.R.
      Diagnosis of human preimplantation embryo viability.
      ,
      • Sermon K.
      • Capalbo A.
      • Cohen J.
      • Coonen E.
      • De Rycke M.
      • De Vos A.
      • Delhanty J.
      • Fiorentino F.
      • Gleicher N.
      • Griesinger G.
      • Grifo J.
      • Handyside A.
      • Harper J.
      • Kokkali G.
      • Mastenbroek S.
      • Meldrum D.
      • Meseguer M.
      • Montag M.
      • Munné S.
      • Rienzi L.
      • Rubio C.
      • Scott K.
      • Scott R.
      • Simon C.
      • Swain J.
      • Treff N.
      • Ubaldi F.
      • Vassena R.
      • Vermeesch J.R.
      • Verpoest W.
      • Wells D.
      • Geraedts J.
      The why, the how and the when of PGS 2.0: current practices and expert opinions of fertility specialists, molecular biologists, and embryologists.
      ). Therefore, the development of a non-invasive, rapid, and cheaper method for assessing embryo ploidy status would represent a breakthrough in the field of IVF (
      • Gardner D.K.
      • Meseguer M.
      • Rubio C.
      • Treff N.R.
      Diagnosis of human preimplantation embryo viability.
      ). The recent implementation of time-lapse devices in more IVF laboratories, allowing continuous embryo monitoring in stable culture conditions, has raised hopes among many embryologists. Although the clinical value of this strategy has been validated in some studies (
      • Petersen B.M.
      • Boel M.
      • Montag M.
      • Gardner D.K.
      Development of a generally applicable morphokinetic algorithm capable of predicting the implantation potential of embryos transferred on Day 3.
      ,
      • Rubio I.
      • Galan A.
      • Larreategui Z.
      • Ayerdi F.
      • Bellver J.
      • Herrero J.
      • Meseguer M.
      Clinical validation of embryo culture and selection by morphokinetic analysis: a randomized, controlled trial of the EmbryoScope.
      ), literature reviews have provided various results (
      • Armstrong S.
      • Arroll N.
      • Cree L.M.
      • Jordan V.
      • Farquhar C.
      Time-lapse systems for embryo incubation and assessment in assisted reproduction.
      ,
      • Chen M.
      • Wei S.
      • Hu J.
      • Yuan J.
      • Liu F.
      Does time-lapse imaging have favorable results for embryo incubation and selection compared with conventional methods in clinical in vitro fertilization? A meta-analysis and systematic review of randomized controlled trials.
      ), leading to ongoing debate on this topic (
      • Harper J.
      • Jackson E.
      • Sermon K.
      • Aitken R.J.
      • Harbottle S.
      • Mocanu E.
      • Hardarson T.
      • Mathur R.
      • Viville S.
      • Vail A.
      • Lundin K.
      Adjuncts in the IVF laboratory: where is the evidence for ‘add-on’ interventions?.
      ). Among the numerous studies reported on time-lapse, some have evaluated the association between morphokinetic parameters and embryo ploidy to evaluate if time lapse could be the awaited non-invasive method for embryo aneuploidy screening. These studies provided discordant conclusions. They were conducted in various settings, with heterogeneous design, procedures and populations, ultimately failing to yield a firm conclusion.
      Therefore, the aim of this study was to conduct a comprehensive review of the literature on the predictive value of morphokinetic parameters for embryo ploidy status.

      Materials and methods

      We conducted a systematic search on Medline of all articles related to time-lapse (or morphokinetic) analysis of human preimplantation embryo development and its association with aneuploidy evaluated with PGS technology published up to April 2017 using the Pubmed database with the following keywords: time-lapse, morphokinetic, aneuploidy, IVF, preimplantation genetic screening, PGS and chromosomal status.
      This search was conducted according to Prisma guidelines (http://www.prisma-statement.org/), and only full-length articles in English dealing with clinical observations in humans were included. The principal summary measure was the predictive value of time-lapse parameters for embryo ploidy. Comparison with a control group was not mandatory. No statistical tests were carried out with these data. All references were screened, and eligibility assessed by two independent reviewers (AR and JL). A third author (TF) checked the final list of references and made the final decision in case of disagreement.
      The following data were extracted from the selected articles: study design, number of couples, clinical indication for PGS, number of embryos, embryo stage for biopsy, PGS technique, time-lapse device, embryo culture atmosphere, morphokinetic parameters studied, euploidy rate, clinical outcome measure, adjustment with patients' characteristics, relevant morphokinetic variables identified, statistical approach and main conclusion.

      Results

      A total of 161 studies were screened for eligibility. All records were screened, and 148 were excluded. A total of 15 full-text articles were assessed in detail for eligibility, among which two were excluded because they were conducted in preimplantation genetic diagnosis cycles rather than in PGS cycles, thus not allowing full information on embryo ploidy status to be obtained. Finally, 13 were selected for data collection on the predictive value of morphokinetic analysis for human embryo ploidy (
      • Balakier H.
      • Sojecki A.
      • Motamedi G.
      • Librach C.
      Impact of multinucleated blastomeres on embryo developmental competence, morphokinetics, and aneuploidy.
      ,
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      ,
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      ,
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      ,
      • Chavez S.L.
      • Loewke K.E.
      • Han J.
      • Moussavi F.
      • Colls P.
      • Munne S.
      • Behr B.
      • Reijo Pera R.A.
      Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage.
      ,
      • Chawla M.
      • Fakih M.
      • Shunnar A.
      • Bayram A.
      • Hellani A.
      • Perumal V.
      • Divakaran J.
      • Budak E.
      Morphokinetic analysis of cleavage stage embryos and its relationship to aneuploidy in a retrospective time-lapse imaging study.
      ,
      • Del Carmen Nogales M.
      • Bronet F.
      • Basile N.
      • Martinez E.M.
      • Linan A.
      • Rodrigo L.
      • Meseguer M.
      Type of chromosome abnormality affects embryo morphology dynamics.
      ,
      • Kramer Y.G.
      • Kofinas J.D.
      • Melzer K.
      • Noyes N.
      • McCaffrey C.
      • Buldo-Licciardi J.
      • McCulloh D.H.
      • Grifo J.A.
      Assessing morphokinetic parameters via time lapse microscopy (TLM) to predict euploidy: are aneuploidy risk classification models universal?.
      ,
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ,
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      ,
      • Patel D.V.
      • Shah P.B.
      • Kotdawala A.P.
      • Herrero J.
      • Rubio I.
      • Banker M.R.
      Morphokinetic behavior of euploid and aneuploid embryos analyzed by time-lapse in embryoscope.
      ,
      • Rienzi L.
      • Capalbo A.
      • Stoppa M.
      • Romano S.
      • Maggiulli R.
      • Albricci L.
      • Scarica C.
      • Farcomeni A.
      • Vajta G.
      • Ubaldi F.M.
      No evidence of association between blastocyst aneuploidy and morphokinetic assessment in a selected population of poor-prognosis patients: a longitudinal cohort study.
      ,
      • Yang Z.
      • Zhang J.
      • Salem S.A.
      • Liu X.
      • Kuang Y.
      • Salem R.D.
      • Liu J.
      Selection of competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for patients undergoing preimplantation genetic screening: a prospective study with sibling oocytes.
      ) (Table 1).
      Table 1Principal characteristics of the studies reporting on the value of morphokinetic parameters as predictors of embryo ploidy. Studies are listed in chronological order.
      Study designNumber of couple/ cyclesClinical indication for PGSNumber of embryosEmbryo stage for biopsyPGS techniqueTime- lapse deviceAtmosphere
      • Chavez S.L.
      • Loewke K.E.
      • Han J.
      • Moussavi F.
      • Colls P.
      • Munne S.
      • Behr B.
      • Reijo Pera R.A.
      Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage.
      Prospective on donated zygotes45/NANA53Day 2aCGHcustom-built miniature microscope system6% CO2, 5% O2
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      Retrospective25/25AMA, RIF, recurrent miscarriage, severe male factor98BlastocystaCGH or SNP arrayEmbryoscope®5.5% CO2, 5% O2
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      Retrospective/validation study69/69Unknown88BlastocystaCGH or SNP arrayEmbryoscope®5.5% CO2, 5% O2
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      Retrospective87/125RIF and recurrent miscarriage504Day 3aCGHEmbryoscope®Not described
      • Kramer Y.G.
      • Kofinas J.D.
      • Melzer K.
      • Noyes N.
      • McCaffrey C.
      • Buldo-Licciardi J.
      • McCulloh D.H.
      • Grifo J.A.
      Assessing morphokinetic parameters via time lapse microscopy (TLM) to predict euploidy: are aneuploidy risk classification models universal?.
      Retrospective/validation study25/25Recurrent miscarriage, AMA, others149BlastocystaCGHEmbryoscope®6% CO2, 5% O2
      • Yang Z.
      • Zhang J.
      • Salem S.A.
      • Liu X.
      • Kuang Y.
      • Salem R.D.
      • Liu J.
      Selection of competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for patients undergoing preimplantation genetic screening: a prospective study with sibling oocytes.
      ProspectiveNARPL, RIF, PCA285BlastocystaCGHEmbryoscope®6% CO2, 5% O2
      • Chawla M.
      • Fakih M.
      • Shunnar A.
      • Bayram A.
      • Hellani A.
      • Perumal V.
      • Divakaran J.
      • Budak E.
      Morphokinetic analysis of cleavage stage embryos and its relationship to aneuploidy in a retrospective time-lapse imaging study.
      Retrospective132/132Sex selection460Day 3aCGHEmbryoscope®Not described
      • Rienzi L.
      • Capalbo A.
      • Stoppa M.
      • Romano S.
      • Maggiulli R.
      • Albricci L.
      • Scarica C.
      • Farcomeni A.
      • Vajta G.
      • Ubaldi F.M.
      No evidence of association between blastocyst aneuploidy and morphokinetic assessment in a selected population of poor-prognosis patients: a longitudinal cohort study.
      Retrospective/validation study138/138AMA, RIF, recurrent miscarriage455BlastocystaCGHEmbryoscope®6% CO2, 5% O2
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      Retrospective444/530Unknown1730/928 cultured in time-lapseBlastocystaCGHEmbryoscope®6% CO2, 5% O2
      • Balakier H.
      • Sojecki A.
      • Motamedi G.
      • Librach C.
      Impact of multinucleated blastomeres on embryo developmental competence, morphokinetics, and aneuploidy.
      Retrospective296 (113 with PGS)/296 (113)AMA, PCOS, male factor and others2441/607 with PGSBlastocystaCGHEmbryoscope®6% CO2, 5% O2
      • Patel D.V.
      • Shah P.B.
      • Kotdawala A.P.
      • Herrero J.
      • Rubio I.
      • Banker M.R.
      Morphokinetic behavior of euploid and aneuploid embryos analyzed by time-lapse in embryoscope.
      Retrospective26/29AMA, RIF, recurrent miscarriage167Day 3aCGHEmbryoscope®Not described
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      Retrospective/validation study103/103AMA, PGD415BlastocystaCGHEmbryoscope®6.8% CO2, 5% O2
      • Del Carmen Nogales M.
      • Bronet F.
      • Basile N.
      • Martinez E.M.
      • Linan A.
      • Rodrigo L.
      • Meseguer M.
      Type of chromosome abnormality affects embryo morphology dynamics.
      Retrospective112/112AMA, RIF and recurrent miscarriage485Day 3aCGHEmbryoscope®Not described
      Euploidy rate (%)Clinical outcome measuresMorphokinetic parameters studiedRelevant morphokinetic variablesAdjusted with patients' characteristicsStatistical approachConclusion
      • Chavez S.L.
      • Loewke K.E.
      • Han J.
      • Moussavi F.
      • Colls P.
      • Munne S.
      • Behr B.
      • Reijo Pera R.A.
      Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage.
      24.5NAAll up to day 2cc2, s2NoMean comparisonCell-cycle parameters could be diagnostic of ploidy and have clinical relevance.
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      38.8NAAll up to blastocyst stagetSB, tBNoMean comparison; Fisher's test; decision-tree modelLate time-lapse parameters increase the probability of selecting euploid embryos.
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      NA
      Validation study conducted in non-PGS cycles.
      CPR and LBRAll up to blastocyst stagetSB, tBNoDecision-tree modelLate time-lapse parameters increases the probability of selecting euploid embryos.
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      28.3Implantation rate and CPRAll up to day 3t5, t5–t2, cc3NoMean comparison; quartiles; logistic regression; ROC curve; decision treeTime-lapse-based algorithm increases the probability of selecting euploid embryos.
      • Kramer Y.G.
      • Kofinas J.D.
      • Melzer K.
      • Noyes N.
      • McCaffrey C.
      • Buldo-Licciardi J.
      • McCulloh D.H.
      • Grifo J.A.
      Assessing morphokinetic parameters via time lapse microscopy (TLM) to predict euploidy: are aneuploidy risk classification models universal?.
      43NAAll up to blastocyst stageNoneNoChi-squared ; ANOVA, ROC curveFailure of Campbell's model. Time-lapse parameters cannot be used to select euploid blastocysts
      • Yang Z.
      • Zhang J.
      • Salem S.A.
      • Liu X.
      • Kuang Y.
      • Salem R.D.
      • Liu J.
      Selection of competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for patients undergoing preimplantation genetic screening: a prospective study with sibling oocytes.
      46Implantation rate, OPRAll up to blastocyst stageNoneNoMean and frequency comparisonTime-lapse increases the probability of non-invasively selecting normal embryos.
      • Chawla M.
      • Fakih M.
      • Shunnar A.
      • Bayram A.
      • Hellani A.
      • Perumal V.
      • Divakaran J.
      • Budak E.
      Morphokinetic analysis of cleavage stage embryos and its relationship to aneuploidy in a retrospective time-lapse imaging study.
      42.8NAAll up to day 3t5–t2, cc3NoMean and frequency comparison; logistic regression; ROC curveTime-lapse increases the probability of non-invasively selecting normal embryos.
      • Rienzi L.
      • Capalbo A.
      • Stoppa M.
      • Romano S.
      • Maggiulli R.
      • Albricci L.
      • Scarica C.
      • Farcomeni A.
      • Vajta G.
      • Ubaldi F.M.
      No evidence of association between blastocyst aneuploidy and morphokinetic assessment in a selected population of poor-prognosis patients: a longitudinal cohort study.
      40.9OPR and LBRAll up to blastocyst stageNoneYesBivariate generalized mixed models, linear logistic modelFailure of Campbell and Basile's models. Time-lapse parameters Cannot be used to select euploid blastocysts.
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      34.9CPRAll up to blastocyst stagetSB, tB, tEB, tHBYesMixed logistic models; mixed linear regressionLate time-lapse parameters are different in euploid and aneuploidy embryos but do not improve clinical outcome.
      • Balakier H.
      • Sojecki A.
      • Motamedi G.
      • Librach C.
      Impact of multinucleated blastomeres on embryo developmental competence, morphokinetics, and aneuploidy.
      49.8Implantation rate, CPR and LBRAll up to blastocyst stage plus multinucleation at two- and four-cell stagesNAYesMean comparison, logistic regressionHigh implantation rate, even for embryos with multinucleation at the two-cell stage.
      • Patel D.V.
      • Shah P.B.
      • Kotdawala A.P.
      • Herrero J.
      • Rubio I.
      • Banker M.R.
      Morphokinetic behavior of euploid and aneuploid embryos analyzed by time-lapse in embryoscope.
      24.5NAAll up to blastocyst staget5–t2, cc3NoMean comparison; chi squared; quartiles; logistic regression; ROC curveTime-lapse-based algorithm (
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      ) increases the probability of selecting euploid embryos but should not replace PGS.
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      41.7NAAll up to blastocyst staget9, tM, tSB, tB, tEBYesClustered data analysisFailure of most models and late time-lapse parameters to predict euploidy.
      • Del Carmen Nogales M.
      • Bronet F.
      • Basile N.
      • Martinez E.M.
      • Linan A.
      • Rodrigo L.
      • Meseguer M.
      Type of chromosome abnormality affects embryo morphology dynamics.
      38.1NAAll up to day 3t3, t5–t2NoMean comparison; chi squared; quartiles; logistic regression analysisTime-lapse is useful to discard embryos with high risk of complex aneuploidies.
      aCGH, array comparative genetic hybridization; AMA, advanced maternal age; ANOVA, analysis of variance; CPR, clinical pregnancy rate; LBR: live birth rate; NA, not applicable; OPR, ongoing pregnancy rate; PCA, previous aneuploidy conceptions; PCOS, polycystic ovary syndrome; PGD, preimplantation genetic diagnosis; PGS, preimplantation genetic screening; RIF, recurrent implantation failure; ROC, receiver operatory characteristic; SNP, single nucleotide polymorphism.
      a Validation study conducted in non-PGS cycles.
      Most studies were retrospective. Only two were prospective, with one conducted on embryos donated for research (
      • Chavez S.L.
      • Loewke K.E.
      • Han J.
      • Moussavi F.
      • Colls P.
      • Munne S.
      • Behr B.
      • Reijo Pera R.A.
      Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage.
      ) and the other one on clinical cycles (
      • Yang Z.
      • Zhang J.
      • Salem S.A.
      • Liu X.
      • Kuang Y.
      • Salem R.D.
      • Liu J.
      Selection of competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for patients undergoing preimplantation genetic screening: a prospective study with sibling oocytes.
      ). The number of couples and IVF–PGS cycles included in these studies varied significantly, ranging from 25 (
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      ) to 444 (
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ), and from 25 (
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      ) to 530 (
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ), respectively. Similarly, the number of embryos included in the analysis was heterogeneous in these studies, ranging from 53 (
      • Chavez S.L.
      • Loewke K.E.
      • Han J.
      • Moussavi F.
      • Colls P.
      • Munne S.
      • Behr B.
      • Reijo Pera R.A.
      Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage.
      ) to 928 (
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ).
      The clinical indication for PGS varied notably among these studies, even if most of them were conventional PGS cases, i.e. advanced maternal age, recurrent implantation failure and recurrent miscarriage. Only one study was conducted in PGS cycles for sex selection (
      • Chawla M.
      • Fakih M.
      • Shunnar A.
      • Bayram A.
      • Hellani A.
      • Perumal V.
      • Divakaran J.
      • Budak E.
      Morphokinetic analysis of cleavage stage embryos and its relationship to aneuploidy in a retrospective time-lapse imaging study.
      ) and one in couples with previous aneuploidy conceptions (
      • Yang Z.
      • Zhang J.
      • Salem S.A.
      • Liu X.
      • Kuang Y.
      • Salem R.D.
      • Liu J.
      Selection of competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for patients undergoing preimplantation genetic screening: a prospective study with sibling oocytes.
      ). Two studies included cases of PGS for severe male factor infertility in addition to conventional PGS indications (
      • Balakier H.
      • Sojecki A.
      • Motamedi G.
      • Librach C.
      Impact of multinucleated blastomeres on embryo developmental competence, morphokinetics, and aneuploidy.
      ,
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      ). Clinical indication for PGS could not be found in two studies (
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      ,
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ).
      Embryo biopsy was carried out at cleavage stage in five studies (
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      ,
      • Chavez S.L.
      • Loewke K.E.
      • Han J.
      • Moussavi F.
      • Colls P.
      • Munne S.
      • Behr B.
      • Reijo Pera R.A.
      Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage.
      ,
      • Chawla M.
      • Fakih M.
      • Shunnar A.
      • Bayram A.
      • Hellani A.
      • Perumal V.
      • Divakaran J.
      • Budak E.
      Morphokinetic analysis of cleavage stage embryos and its relationship to aneuploidy in a retrospective time-lapse imaging study.
      ,
      • Del Carmen Nogales M.
      • Bronet F.
      • Basile N.
      • Martinez E.M.
      • Linan A.
      • Rodrigo L.
      • Meseguer M.
      Type of chromosome abnormality affects embryo morphology dynamics.
      ,
      • Patel D.V.
      • Shah P.B.
      • Kotdawala A.P.
      • Herrero J.
      • Rubio I.
      • Banker M.R.
      Morphokinetic behavior of euploid and aneuploid embryos analyzed by time-lapse in embryoscope.
      ) and at the blastocyst stage in eight studies (
      • Balakier H.
      • Sojecki A.
      • Motamedi G.
      • Librach C.
      Impact of multinucleated blastomeres on embryo developmental competence, morphokinetics, and aneuploidy.
      ,
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      ,
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      ,
      • Kramer Y.G.
      • Kofinas J.D.
      • Melzer K.
      • Noyes N.
      • McCaffrey C.
      • Buldo-Licciardi J.
      • McCulloh D.H.
      • Grifo J.A.
      Assessing morphokinetic parameters via time lapse microscopy (TLM) to predict euploidy: are aneuploidy risk classification models universal?.
      ,
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ,
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      ,
      • Rienzi L.
      • Capalbo A.
      • Stoppa M.
      • Romano S.
      • Maggiulli R.
      • Albricci L.
      • Scarica C.
      • Farcomeni A.
      • Vajta G.
      • Ubaldi F.M.
      No evidence of association between blastocyst aneuploidy and morphokinetic assessment in a selected population of poor-prognosis patients: a longitudinal cohort study.
      ,
      • Yang Z.
      • Zhang J.
      • Salem S.A.
      • Liu X.
      • Kuang Y.
      • Salem R.D.
      • Liu J.
      Selection of competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for patients undergoing preimplantation genetic screening: a prospective study with sibling oocytes.
      ). When performed at the cleavage stage, no morphokinetic data were provided on subsequent embryo development, except in one study (
      • Patel D.V.
      • Shah P.B.
      • Kotdawala A.P.
      • Herrero J.
      • Rubio I.
      • Banker M.R.
      Morphokinetic behavior of euploid and aneuploid embryos analyzed by time-lapse in embryoscope.
      ).
      All studies but one (
      • Chavez S.L.
      • Loewke K.E.
      • Han J.
      • Moussavi F.
      • Colls P.
      • Munne S.
      • Behr B.
      • Reijo Pera R.A.
      Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage.
      ) were carried out with the Embryoscope® as time-lapse device. Although unlikely, whether the type of time-lapse device used could influence the eventual association of morphokinetic parameters with embryo ploidy status is not known, as no comparative study has yet been conducted. Although embryo culture atmosphere was not reported in four studies (
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      ,
      • Chawla M.
      • Fakih M.
      • Shunnar A.
      • Bayram A.
      • Hellani A.
      • Perumal V.
      • Divakaran J.
      • Budak E.
      Morphokinetic analysis of cleavage stage embryos and its relationship to aneuploidy in a retrospective time-lapse imaging study.
      ,
      • Del Carmen Nogales M.
      • Bronet F.
      • Basile N.
      • Martinez E.M.
      • Linan A.
      • Rodrigo L.
      • Meseguer M.
      Type of chromosome abnormality affects embryo morphology dynamics.
      ,
      • Patel D.V.
      • Shah P.B.
      • Kotdawala A.P.
      • Herrero J.
      • Rubio I.
      • Banker M.R.
      Morphokinetic behavior of euploid and aneuploid embryos analyzed by time-lapse in embryoscope.
      ), it was carried out under low oxygen tension in the nine remaining studies.
      All studies on PGS technique were based on aCGH, allowing the evaluation of all chromosomes. Only two studies from the same group reported using both aCGH and single nucleotide polymorphism array (
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      ,
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      ). Euploidy rate was reported in 12 studies (not applicable in
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      ), which was conducted in non-PGS cycles) and ranged from 24.5% (
      • Chawla M.
      • Fakih M.
      • Shunnar A.
      • Bayram A.
      • Hellani A.
      • Perumal V.
      • Divakaran J.
      • Budak E.
      Morphokinetic analysis of cleavage stage embryos and its relationship to aneuploidy in a retrospective time-lapse imaging study.
      ) to 49.8% (
      • Balakier H.
      • Sojecki A.
      • Motamedi G.
      • Librach C.
      Impact of multinucleated blastomeres on embryo developmental competence, morphokinetics, and aneuploidy.
      ), with a trend towards higher euploidy rate when biopsy was carried out at the blastocyst stage than at the cleavage stage.
      Six studies included clinical outcome measures after a PGS cycle (
      • Balakier H.
      • Sojecki A.
      • Motamedi G.
      • Librach C.
      Impact of multinucleated blastomeres on embryo developmental competence, morphokinetics, and aneuploidy.
      ,
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      ,
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      ,
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ,
      • Rienzi L.
      • Capalbo A.
      • Stoppa M.
      • Romano S.
      • Maggiulli R.
      • Albricci L.
      • Scarica C.
      • Farcomeni A.
      • Vajta G.
      • Ubaldi F.M.
      No evidence of association between blastocyst aneuploidy and morphokinetic assessment in a selected population of poor-prognosis patients: a longitudinal cohort study.
      ,
      • Yang Z.
      • Zhang J.
      • Salem S.A.
      • Liu X.
      • Kuang Y.
      • Salem R.D.
      • Liu J.
      Selection of competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for patients undergoing preimplantation genetic screening: a prospective study with sibling oocytes.
      ). Most of them used clinical pregnancy rate; some also used implantation rate or live birth rate.
      Concerning the morphokinetic parameters studied, all studies reported morphokinetic parameters up to embryo biopsy, including pronuclei appearance and fading, cellular cleavage timings and intervals, compaction and blastocyst formation and expansion. One study also reported multinucleation at the two-cell and four-cell stages (
      • Balakier H.
      • Sojecki A.
      • Motamedi G.
      • Librach C.
      Impact of multinucleated blastomeres on embryo developmental competence, morphokinetics, and aneuploidy.
      ). Among the 13 selected studies, 11 aimed at identifying relevant morphokinetic variables, which could be significantly different between euploid and aneuploidy groups, and finally help in selecting euploid embryos for transfer, whereas two consisted of external validation of previously published models (
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      ,
      • Kramer Y.G.
      • Kofinas J.D.
      • Melzer K.
      • Noyes N.
      • McCaffrey C.
      • Buldo-Licciardi J.
      • McCulloh D.H.
      • Grifo J.A.
      Assessing morphokinetic parameters via time lapse microscopy (TLM) to predict euploidy: are aneuploidy risk classification models universal?.
      ). Studies conducted in early cleavage embryos mostly identified intervals between cleavages rather than cleavage timings as relevant for identifying euploid embryos (
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      ,
      • Chavez S.L.
      • Loewke K.E.
      • Han J.
      • Moussavi F.
      • Colls P.
      • Munne S.
      • Behr B.
      • Reijo Pera R.A.
      Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage.
      ,
      • Chawla M.
      • Fakih M.
      • Shunnar A.
      • Bayram A.
      • Hellani A.
      • Perumal V.
      • Divakaran J.
      • Budak E.
      Morphokinetic analysis of cleavage stage embryos and its relationship to aneuploidy in a retrospective time-lapse imaging study.
      ,
      • Del Carmen Nogales M.
      • Bronet F.
      • Basile N.
      • Martinez E.M.
      • Linan A.
      • Rodrigo L.
      • Meseguer M.
      Type of chromosome abnormality affects embryo morphology dynamics.
      ,
      • Patel D.V.
      • Shah P.B.
      • Kotdawala A.P.
      • Herrero J.
      • Rubio I.
      • Banker M.R.
      Morphokinetic behavior of euploid and aneuploid embryos analyzed by time-lapse in embryoscope.
      ). Some studies conducted at the blastocyst stage identified late morphokinetic parameters, i.e. compaction or blastulation stages, but not early ones (cleavage stages) as relevant predictors of embryo ploidy (
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      ,
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ,
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      ). Not all studies, however, conducted at the blastocyst stage reported significant morphokinetic differences between euploid and aneuploid embryos (
      • Rienzi L.
      • Capalbo A.
      • Stoppa M.
      • Romano S.
      • Maggiulli R.
      • Albricci L.
      • Scarica C.
      • Farcomeni A.
      • Vajta G.
      • Ubaldi F.M.
      No evidence of association between blastocyst aneuploidy and morphokinetic assessment in a selected population of poor-prognosis patients: a longitudinal cohort study.
      ,
      • Yang Z.
      • Zhang J.
      • Salem S.A.
      • Liu X.
      • Kuang Y.
      • Salem R.D.
      • Liu J.
      Selection of competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for patients undergoing preimplantation genetic screening: a prospective study with sibling oocytes.
      ).
      In addition to the studies aimed at identifying predictive morphokinetic markers, other investigators have conducted external validation of some previously published morphokinetic models. The model by
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      was evaluated externally by
      • Kramer Y.G.
      • Kofinas J.D.
      • Melzer K.
      • Noyes N.
      • McCaffrey C.
      • Buldo-Licciardi J.
      • McCulloh D.H.
      • Grifo J.A.
      Assessing morphokinetic parameters via time lapse microscopy (TLM) to predict euploidy: are aneuploidy risk classification models universal?.
      and by themselves in a separate cohort (
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      ).
      • Patel D.V.
      • Shah P.B.
      • Kotdawala A.P.
      • Herrero J.
      • Rubio I.
      • Banker M.R.
      Morphokinetic behavior of euploid and aneuploid embryos analyzed by time-lapse in embryoscope.
      tested the performance of the model by
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      .
      • Rienzi L.
      • Capalbo A.
      • Stoppa M.
      • Romano S.
      • Maggiulli R.
      • Albricci L.
      • Scarica C.
      • Farcomeni A.
      • Vajta G.
      • Ubaldi F.M.
      No evidence of association between blastocyst aneuploidy and morphokinetic assessment in a selected population of poor-prognosis patients: a longitudinal cohort study.
      and
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      tested the performance of both Campbell's and Basile's models, both concluding that the models failed to predict embryo euploidy.
      Statistical approach varied greatly among these 13 studies, depending on the main outcome measure and study design. Most studies performed basic univariate analysis to compare morphokinetic parameters in euploid and aneuploid embryos. Most studies also carried out logistic regression analysis to identify some independent predictors of embryo ploidy, eventually integrated in a predictive model. The sensitivity and specificity of the model was then evaluated with receiver operator characteristic curve analysis when appropriate (
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      ,
      • Chawla M.
      • Fakih M.
      • Shunnar A.
      • Bayram A.
      • Hellani A.
      • Perumal V.
      • Divakaran J.
      • Budak E.
      Morphokinetic analysis of cleavage stage embryos and its relationship to aneuploidy in a retrospective time-lapse imaging study.
      ,
      • Kramer Y.G.
      • Kofinas J.D.
      • Melzer K.
      • Noyes N.
      • McCaffrey C.
      • Buldo-Licciardi J.
      • McCulloh D.H.
      • Grifo J.A.
      Assessing morphokinetic parameters via time lapse microscopy (TLM) to predict euploidy: are aneuploidy risk classification models universal?.
      ,
      • Patel D.V.
      • Shah P.B.
      • Kotdawala A.P.
      • Herrero J.
      • Rubio I.
      • Banker M.R.
      Morphokinetic behavior of euploid and aneuploid embryos analyzed by time-lapse in embryoscope.
      ). Importantly, few authors emphasized the possible bias of considering embryos as individuals in statistical analysis, as all embryos originating from the same patient are influenced by those patient-specific characteristics and are, therefore, not independent entities (‘cohort effect’). Therefore, these investigators strongly recommended the adjustment of statistical analysis and its results with patient characteristics (
      • Kirkegaard K.
      • Sundvall L.
      • Erlandsen M.
      • Hindkjaer J.J.
      • Knudsen U.B.
      • Ingerslev H.J.
      Timing of human preimplantation embryonic development is confounded by embryo origin.
      ,
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      ).
      Finally, most, but not all, investigators reported significant differences in morphokinetic pattern between euploid and aneuploid embryos, but the clinical significance of these results was absent to modest (Table 1). Although the conclusions raised by investigators varied significantly, all concluded that time-lapse should not be considered as an appropriate non-invasive method for embryo ploidy assessment.

      Discussion

      This comprehensive review of the literature on the effectiveness of time-lapse as a predictor of embryo ploidy highlights the large heterogeneity of the studies published to date, concluding that neither a unique morphokinetic nor combined parameters could predict embryo ploidy with enough sensitivity, specificity, or both, to be used clinically for embryo selection.
      First, most studies reviewed here were carried out retrospectively and within a single clinic, with different sample sizes. Although this does not necessarily lessen their value, there is a need for large multi-centre studies to enhance the overall quality of the evidence generated.
      The second question raised in this review concerns the type of time-lapse device. Although this should theoretically not lead to a significant difference in measuring morphokinetic parameters, it should be noted that all studies, bar one, were conducted with the Embryoscope®, the first and most widely implemented time-lapse device to date, thus providing a certain inter-study homogeneity on technical aspects. Whether the use of different approaches, as well as devices and analytical methods, in the field of time-lapse could account for the conflicting findings found within the literature is hard to determine and quantify precisely. This should be explored in further studies. The issue of inter-operator variability in annotating morphokinetic parameters could eventually be raised, thus encouraging the development of automated annotation tools (
      • Castello D.
      • Motato Y.
      • Basile N.
      • Remohi J.
      • Espejo-Catena M.
      • Meseguer M.
      How much have we learned from time-lapse in clinical IVF?.
      ,
      • Molder A.
      • Drury S.
      • Costen N.
      • Hartshorne G.M.
      • Czanner S.
      Semiautomated analysis of embryoscope images: using localized variance of image intensity to detect embryo developmental stages.
      ). Although this variability has been shown to be low (
      • Sundvall L.
      • Ingerslev H.J.
      • Breth Knudsen U.
      • Kirkegaard K.
      Inter- and intra-observer variability of time-lapse annotations.
      ), it is unclear how widely guidelines for annotation practice (
      • Ciray H.N.
      • Campbell A.
      • Agerholm I.E.
      • Aguilar J.
      • Chamayou S.
      • Esbert M.
      • Sayed S.
      Time-Lapse User Group.
      Proposed guidelines on the nomenclature and annotation of dynamic human embryo monitoring by a time-lapse user group.
      ) are followed and how consistent time-lapse users are in their operating procedures. Whether more recent time-lapse devices with automated detection of cell cleavages will provide different results and lead to different conclusions still needs to be tested.
      Although the clinical indication for PGS varied notably among the studies, the main indications were advanced maternal age, recurrent implantation failure and recurrent miscarriage. It is, therefore unlikely that differences in clinical indications would explain the discrepancy in conclusions of the studies cited here. Some patient characteristics, however, have been shown by some investigators to be critical for interpretating morphokinetic studies, as embryos from the same patient tend to cluster (
      • Kirkegaard K.
      • Sundvall L.
      • Erlandsen M.
      • Hindkjaer J.J.
      • Knudsen U.B.
      • Ingerslev H.J.
      Timing of human preimplantation embryonic development is confounded by embryo origin.
      ,
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      ). This point will be discussed further in the discussion.
      The most significant difference between the studies reviewed here was the stage at which embryo biopsy was carried out. Indeed, embryo biopsy was carried out at the cleavage stage in five studies (
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      ,
      • Chavez S.L.
      • Loewke K.E.
      • Han J.
      • Moussavi F.
      • Colls P.
      • Munne S.
      • Behr B.
      • Reijo Pera R.A.
      Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage.
      ,
      • Chawla M.
      • Fakih M.
      • Shunnar A.
      • Bayram A.
      • Hellani A.
      • Perumal V.
      • Divakaran J.
      • Budak E.
      Morphokinetic analysis of cleavage stage embryos and its relationship to aneuploidy in a retrospective time-lapse imaging study.
      ,
      • Del Carmen Nogales M.
      • Bronet F.
      • Basile N.
      • Martinez E.M.
      • Linan A.
      • Rodrigo L.
      • Meseguer M.
      Type of chromosome abnormality affects embryo morphology dynamics.
      ,
      • Patel D.V.
      • Shah P.B.
      • Kotdawala A.P.
      • Herrero J.
      • Rubio I.
      • Banker M.R.
      Morphokinetic behavior of euploid and aneuploid embryos analyzed by time-lapse in embryoscope.
      ), whereas embryo biopsy was carried out at the blastocyst stage in eight studies (
      • Balakier H.
      • Sojecki A.
      • Motamedi G.
      • Librach C.
      Impact of multinucleated blastomeres on embryo developmental competence, morphokinetics, and aneuploidy.
      ,
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      ,
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      ,
      • Kramer Y.G.
      • Kofinas J.D.
      • Melzer K.
      • Noyes N.
      • McCaffrey C.
      • Buldo-Licciardi J.
      • McCulloh D.H.
      • Grifo J.A.
      Assessing morphokinetic parameters via time lapse microscopy (TLM) to predict euploidy: are aneuploidy risk classification models universal?.
      ,
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ,
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      ,
      • Rienzi L.
      • Capalbo A.
      • Stoppa M.
      • Romano S.
      • Maggiulli R.
      • Albricci L.
      • Scarica C.
      • Farcomeni A.
      • Vajta G.
      • Ubaldi F.M.
      No evidence of association between blastocyst aneuploidy and morphokinetic assessment in a selected population of poor-prognosis patients: a longitudinal cohort study.
      ,
      • Yang Z.
      • Zhang J.
      • Salem S.A.
      • Liu X.
      • Kuang Y.
      • Salem R.D.
      • Liu J.
      Selection of competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for patients undergoing preimplantation genetic screening: a prospective study with sibling oocytes.
      ). The respective advantages and disadvantages of these two strategies have been debated in recent years (
      • Scott Jr., R.T.
      • Upham K.M.
      • Forman E.J.
      • Zhao T.
      • Treff N.R.
      Cleavage-stage biopsy significantly impairs human embryonic implantation potential while blastocyst biopsy does not: a randomized and paired clinical trial.
      ,
      • Sermon K.
      • Capalbo A.
      • Cohen J.
      • Coonen E.
      • De Rycke M.
      • De Vos A.
      • Delhanty J.
      • Fiorentino F.
      • Gleicher N.
      • Griesinger G.
      • Grifo J.
      • Handyside A.
      • Harper J.
      • Kokkali G.
      • Mastenbroek S.
      • Meldrum D.
      • Meseguer M.
      • Montag M.
      • Munné S.
      • Rienzi L.
      • Rubio C.
      • Scott K.
      • Scott R.
      • Simon C.
      • Swain J.
      • Treff N.
      • Ubaldi F.
      • Vassena R.
      • Vermeesch J.R.
      • Verpoest W.
      • Wells D.
      • Geraedts J.
      The why, the how and the when of PGS 2.0: current practices and expert opinions of fertility specialists, molecular biologists, and embryologists.
      ). Trophectoderm biopsy, however, has gained increasing interest, and is more widely used, as it is considered to optimize the whole procedure when fewer embryos are available, but with higher implantation potential than cleavage stage biopsy (
      • Sermon K.
      • Capalbo A.
      • Cohen J.
      • Coonen E.
      • De Rycke M.
      • De Vos A.
      • Delhanty J.
      • Fiorentino F.
      • Gleicher N.
      • Griesinger G.
      • Grifo J.
      • Handyside A.
      • Harper J.
      • Kokkali G.
      • Mastenbroek S.
      • Meldrum D.
      • Meseguer M.
      • Montag M.
      • Munné S.
      • Rienzi L.
      • Rubio C.
      • Scott K.
      • Scott R.
      • Simon C.
      • Swain J.
      • Treff N.
      • Ubaldi F.
      • Vassena R.
      • Vermeesch J.R.
      • Verpoest W.
      • Wells D.
      • Geraedts J.
      The why, the how and the when of PGS 2.0: current practices and expert opinions of fertility specialists, molecular biologists, and embryologists.
      ). Moreover, it allows the biopsy of several cells and probably allows a better management of embryo mosaicism (
      • Capalbo A.
      • Bono S.
      • Spizzichino L.
      • Biricik A.
      • Baldi M.
      • Colamaria S.
      • Ubaldi F.M.
      • Rienzi L.
      • Fiorentino F.
      Sequential comprehensive chromosome analysis on polar bodies, blastomeres and trophoblast: insights into female meiotic errors and chromosomal segregation in the preimplantation window of embryo development.
      ). Whether trophectoderm biopsy is more relevant than cleavage stage biopsy for PGS was not the topic of this review. Recent data, however, obtained in arrested embryos cultured in time-lapse device and extensively analysed by genome-wide SNP genotyping in both polar bodies and karyomapping of disaggregated embryonic cells, suggest that genomic imbalance and partial genome loss occurring during early cleavage affects embryonic gene expression and blocks the morula to blastocyst transition (
      • Ottolini C.S.
      • Kitchen J.
      • Xanthopoulou L.
      • Gordon T.
      • Summers M.C.
      • Handyside A.H.
      Tripolar mitosis and partitioning of the genome arrests human preimplantation development in vitro.
      ). This reinforces the value of trophectoderm biopsy compared with performing biopsy pre-zygote genome activation at the cleavage stages of development. The present comprehensive review of the literature could eventually be repeated and specifically focus on morphokinetic follow-up up to the blastocyst stage followed by trophectoderm biopsy when more studies are available.
      Various technical approaches can be used for PGS. Here, all studies were based on aCGH, with two of them also using single nucleotide polymorphism array
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      ,
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      . Whether the implementation of new technologies for embryo aneuploidy screening, such as next-generation sequencing, brings new insights into the association between morphokinetic parameters and embryo ploidy should be explored in further studies.
      Embryo culture conditions could constitute a bias in assessing morphokinetics. Indeed, low oxygen tension has been shown to result in significantly different morphokinetic patterns (
      • Kirkegaard K.
      • Sundvall L.
      • Erlandsen M.
      • Hindkjaer J.J.
      • Knudsen U.B.
      • Ingerslev H.J.
      Timing of human preimplantation embryonic development is confounded by embryo origin.
      ) than atmospheric ones. Although this was not reported in four studies, most of them included in this review were conducted under low oxygen tension.
      Six studies included clinical outcome measures after PGS cycle (
      • Balakier H.
      • Sojecki A.
      • Motamedi G.
      • Librach C.
      Impact of multinucleated blastomeres on embryo developmental competence, morphokinetics, and aneuploidy.
      ,
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      ,
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      ,
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ,
      • Rienzi L.
      • Capalbo A.
      • Stoppa M.
      • Romano S.
      • Maggiulli R.
      • Albricci L.
      • Scarica C.
      • Farcomeni A.
      • Vajta G.
      • Ubaldi F.M.
      No evidence of association between blastocyst aneuploidy and morphokinetic assessment in a selected population of poor-prognosis patients: a longitudinal cohort study.
      ,
      • Yang Z.
      • Zhang J.
      • Salem S.A.
      • Liu X.
      • Kuang Y.
      • Salem R.D.
      • Liu J.
      Selection of competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for patients undergoing preimplantation genetic screening: a prospective study with sibling oocytes.
      ). Interpreting these data, however, remains hazardous, as none of them was specifically designed to determine the relevance of morphokinetic parameters in predicting clinical outcome after PGS cycle.
      Concerning the type of morphokinetic parameters analysed, studies with trophectoderm biopsy obviously included additional data compared with those conducted in cleavage stage embryos. These studies mostly concluded that intervals between cellular cleavages were more relevant than cleavage timings for the selection of euploid embryos (
      • Basile N.
      • Del Carmen Nogales C.
      • Bronet F.
      • Florensa M.
      • Riqueiros M.
      • Rodrigo L.
      • García-Velasco J.
      • Meseguer M.
      Increasing the probability of selecting chromosomally normal embryos by time-lapse morphokinetics analysis.
      ,
      • Chavez S.L.
      • Loewke K.E.
      • Han J.
      • Moussavi F.
      • Colls P.
      • Munne S.
      • Behr B.
      • Reijo Pera R.A.
      Dynamic blastomere behaviour reflects human embryo ploidy by the four-cell stage.
      ,
      • Chawla M.
      • Fakih M.
      • Shunnar A.
      • Bayram A.
      • Hellani A.
      • Perumal V.
      • Divakaran J.
      • Budak E.
      Morphokinetic analysis of cleavage stage embryos and its relationship to aneuploidy in a retrospective time-lapse imaging study.
      ,
      • Del Carmen Nogales M.
      • Bronet F.
      • Basile N.
      • Martinez E.M.
      • Linan A.
      • Rodrigo L.
      • Meseguer M.
      Type of chromosome abnormality affects embryo morphology dynamics.
      ,
      • Patel D.V.
      • Shah P.B.
      • Kotdawala A.P.
      • Herrero J.
      • Rubio I.
      • Banker M.R.
      Morphokinetic behavior of euploid and aneuploid embryos analyzed by time-lapse in embryoscope.
      ). This value of cellular intervals was previously suggested in clinical studies conducted in IVF cycles aimed at identifying morphokinetic predictors of implantation (
      • Meseguer M.
      • Herrero J.
      • Tejera A.
      • Hilligsoe K.M.
      • Ramsing N.B.
      • Remohi J.
      The use of morphokinetics as a predictor of embryo implantation.
      ). Not all studies carried out at the blastocyst stage reported significant morphokinetic differences between euploid and aneuploid embryos (
      • Rienzi L.
      • Capalbo A.
      • Stoppa M.
      • Romano S.
      • Maggiulli R.
      • Albricci L.
      • Scarica C.
      • Farcomeni A.
      • Vajta G.
      • Ubaldi F.M.
      No evidence of association between blastocyst aneuploidy and morphokinetic assessment in a selected population of poor-prognosis patients: a longitudinal cohort study.
      ,
      • Yang Z.
      • Zhang J.
      • Salem S.A.
      • Liu X.
      • Kuang Y.
      • Salem R.D.
      • Liu J.
      Selection of competent blastocysts for transfer by combining time-lapse monitoring and array CGH testing for patients undergoing preimplantation genetic screening: a prospective study with sibling oocytes.
      ), but most did (
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      ,
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ,
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      ). Interestingly, these studies did not confirm the value of these early parameters as relevant predictors of embryo ploidy (
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      ,
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ,
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      ). As genetic events, such as mitotic errors, genomic imbalance or genome loss, occur during late embryo development after embryo genomic activation (
      • Capalbo A.
      • Bono S.
      • Spizzichino L.
      • Biricik A.
      • Baldi M.
      • Colamaria S.
      • Ubaldi F.M.
      • Rienzi L.
      • Fiorentino F.
      Sequential comprehensive chromosome analysis on polar bodies, blastomeres and trophoblast: insights into female meiotic errors and chromosomal segregation in the preimplantation window of embryo development.
      ,
      • Ottolini C.S.
      • Kitchen J.
      • Xanthopoulou L.
      • Gordon T.
      • Summers M.C.
      • Handyside A.H.
      Tripolar mitosis and partitioning of the genome arrests human preimplantation development in vitro.
      ), this might account for this apparent loss of predictive value of early morphokinetic parameters for embryo ploidy when evaluated at the blastocyst stage. This, however, remains to be confirmed in longitudinal studies with cleavage stage and blastocyst biopsy successively performed.
      Finally, the recently raised issue of statistical approach and adjustment for patients' characteristics to take clustering effect into account in time-lapse studies (
      • Kirkegaard K.
      • Sundvall L.
      • Erlandsen M.
      • Hindkjaer J.J.
      • Knudsen U.B.
      • Ingerslev H.J.
      Timing of human preimplantation embryonic development is confounded by embryo origin.
      ) was also questioned in three studies included in this review (
      • Minasi M.G.
      • Colasante A.
      • Riccio T.
      • Ruberti A.
      • Casciani V.
      • Scarselli F.
      • Spinella F.
      • Fiorentino F.
      • Varricchio M.T.
      • Greco E.
      Correlation between aneuploidy, standard morphology evaluation and morphokinetic development in 1730 biopsied blastocysts: a consecutive case series study.
      ,
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      ,
      • Rienzi L.
      • Capalbo A.
      • Stoppa M.
      • Romano S.
      • Maggiulli R.
      • Albricci L.
      • Scarica C.
      • Farcomeni A.
      • Vajta G.
      • Ubaldi F.M.
      No evidence of association between blastocyst aneuploidy and morphokinetic assessment in a selected population of poor-prognosis patients: a longitudinal cohort study.
      ), and, particularly, in one of them (
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      ). The concept of this approach is that embryos generated from one couple should not be considered individually. Instead, the statistical approach should consider intra-patient clustering effect to determine the extent to which the morphokinetic variation observed is independent of patient's clinical or cycle characteristics (
      • Kirkegaard K.
      • Sundvall L.
      • Erlandsen M.
      • Hindkjaer J.J.
      • Knudsen U.B.
      • Ingerslev H.J.
      Timing of human preimplantation embryonic development is confounded by embryo origin.
      ). In the study by
      • Mumusoglu S.
      • Yarali I.
      • Bozdag G.
      • Ozdemir P.
      • Polat M.
      • Sokmensuer L.K.
      • Yarali H.
      Time-lapse morphokinetic assessment has low to moderate ability to predict euploidy when patient- and ovarian stimulation-related factors are taken into account with the use of clustered data analysis.
      , 16–47% of the observed variation of morphokinetic parameters was found to be patient-related. Interestingly, the investigators concluded that considering embryos as individuals in statistical analysis could represent a major bias, leading to overestimated statistical associations and potentially incorrect conclusions, especially in heterogeneous populations. This was also highlighted in a commentary published in 2014 (
      • Ottolini C.
      • Rienzi L.
      • Capalbo A.
      A cautionary note against embryo aneuploidy risk assessment using time-lapse imaging.
      ), in which the authors comment on the studies reported by
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Hickman C.F.
      Modelling a risk classification of aneuploidy in human embryos using non-invasive morphokinetics.
      ,
      • Campbell A.
      • Fishel S.
      • Bowman N.
      • Duffy S.
      • Sedler M.
      • Thornton S.
      Retrospective analysis of outcomes after IVF using an aneuploidy risk model derived from time-lapse imaging without PGS.
      . The authors of this commentary particularly questioned the reported association between morphokinetic parameters and implantation, as no female age was provided, and insisted on the importance of confounding factors such as age in this non-age-controlled cohort. This was further debated by
      • Campbell A.
      • Fishel S.
      • Laegdsmand M.
      Aneuploidy is a key causal factor of delays in blastulation: author response to ‘A cautionary note against aneuploidy risk assessment using time-lapse imaging’.
      , who stated that age was not the likely causal factor of observed delays in blastulation.

      Conclusion

      This comprehensive review of the literature demonstrates that morphokinetic parameters should not yet be used as a surrogate for PGS to determine chromosomal status of the preimplantation embryo. More large-scale studies, conducted in homogeneous populations with standard culture and biopsy protocol, using relevant statistical approaches adjusted to patients' characteristics, are needed to gain insight into the putative association between embryo morphokinetic parameters and ploidy, ultimately improving IVF clinical outcome.

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      Biography

      Thomas Freour, PharmD, PhD, is the head of the ART Center at the University Hospital of Nantes, France. He is also a member of the UMR1064 research team, co-leading the pluripotency and embryo development group. His main fields of interest are embryology, time-lapse, ovarian reserve, proteomics and sperm physiology.
      Key message
      Studies reporting an association between morphokinetic parameters and embryo ploidy status are controversial and do not support the predictive value of time-lapse analysis for embryo aneuploidy screening.