What is the optimal lead follicle size in letrozole, human menopausal gonadotrophin and intrauterine insemination (IUI) cycles with and without spontaneous LH surges?
This retrospective cohort study included 3797 letrozole HMG IUI cycles between January 2010 and May 2021. All cycles were divided into two groups: the HCG trigger group (trigger day LH ≤15 mIU/ml) and the spontaneous LH surge group (trigger day LH >15 mIU/ml). These two groups were subdivided into smaller groups based on the diameter of the follicles. The primary outcome measure was clinical pregnancy rate. Logistic regression analysis was conducted to explore other risk factors.
In the HCG trigger group, the clinical pregnancy rate varied significantly, with rates of 20.8%, 14.9% and 11.8% for the 16.1–18.0, 18.1–20.0 and 20.1–22.0 mm groups, respectively (P = 0.005). In the spontaneous LH surge group, the pregnancy rate of follicles within 14.1–16.0 mm was significantly higher than that of follicles within 20.1–22.0 mm (adjusted OR 0.533, 95% CI 0.308 to 0.923, P = 0.025). Also, patients with two lead follicles were 2.569 times more likely to achieve a clinical pregnancy than those with only one lead follicle (adjusted OR 2.569, 95% CI 1.258 to 5.246, P = 0.010). The duration of infertility was also found to be a common influencing factor in both groups.
The optimal lead follicle size was between 16.1 and 18.0 mm in HCG-triggered letrozole HMG IUI cycles. If the lead follicle size is relatively small (14.1–18.0 mm) when a spontaneous LH surge occurs, there is no need to cancel the IUI cycle.
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Kuang Yanping MD, PhD, is Director of the Department of Assisted Reproductive Medicine at Shanghai Ninth People's Hospital. He is Chairman of the Professional Committee on Reproductive Health, China Association of Rehabilitation Medicine, and Vice Chairman of the Reproductive Medicine branch, China International Exchange and Promotive Association for Medical and Health Care.
Published online: November 06, 2022
Accepted: November 3, 2022
Received in revised form: September 28, 2022
Received: August 1, 2022Declaration: The authors report no financial or commercial conflicts of interest.
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