Differential optimal follicle sizes for ovulatory dysfunction and unexplained infertility in LE-IUI cycles: a...

This study aims to identify the optimal dominant follicle size on the trigger day in patients with ovulatory dysfunction and unexplained infertility undergoing intrauterine insemination with letrozole (LE-IUI) cycles.

A retrospective analysis included 411 cycles of each group after 1:1 propensity score matching, comparing basic characteristics and outcomes based on dominant follicle size.

Higher rates of HCG positive, clinical pregnancy, and live birth were found in ovulatory dysfunction versus unexplained infertility (22.4% vs. 9.5%; 21.5% vs. 7.9%; 19% vs. 7.1%, P < 0.001). In ovulatory dysfunction, dominant follicles 17-18.9 mm had lower rates of HCG positive (7.6% vs. 21.5% vs. 26.2%, P = 0.007), clinical pregnancy (6.1% vs. 21.5% vs. 25.6%, P = 0.004), and live birth (4.5% vs. 19.2% vs. 23.2%, P = 0.004) compared to 19-21.0 mm and > 21.0 mm groups. Conversely, in unexplained infertility, follicles > 21.0 mm had lower HCG positive rate(13.3% vs. 11.8% vs. 3.4%, P = 0.023) compare to other two groups. Dominant follicle size on trigger day influenced HCG positive rate in LE-IUI cycles for both groups.

Triggering at follicle size ≥ 19.0 mm may be optimal for ovulatory dysfunction, while a size ≤ 21 mm may improve HCG positive rates in unexplained infertility, underscoring the need to consider infertility factors in trigger decisions.

This study is registered with China Medical Research Online (Registration Number: MR-44-23-038090S, www.medicalresearch.org.cn ).