Effect of time between human chorionic gonadotropin injection and egg retrieval is age dependent

Objective: To investigate whether egg retrieval at ≥36.5 hours improves IVF outcomes in women aged ≥40 years.

Design: Retrospective cohort study.

Setting: Academic medical center.

Patient(s): First-attempt autologous IVF cycles without preimplantation genetic diagnosis, IUI conversion, or intentional delayed egg retrieval were included (n=3,231). Cycles were stratified by age and hCG exposure (<36.5 vs. ≥36.5 hours).

Intervention(s): None.

Main outcome measure(s): Oocyte yield, maturity, fertilization, embryo quality, implantation, clinical pregnancy, and live birth were analyzed, controlling for age and gonadotropins. Stimulation type, hMG use, stimulation days, day-3 FSH level, and diagnosis were evaluated as potential confounders. Multivariable regression analyses were performed and Wald tests for trend calculated.

Result(s): No consistent differences in oocyte yield, maturity, fertilization, or embryo quality were detected. No absolute differences in outcomes were noted among group comparisons. However, as age increased, significant trends toward improved implantation, clinical pregnancy, and live birth were detected at ≥36.5 hours.

Conclusion(s): Extending exposure to hCG for ≥36.5 hours may be beneficial in patients aged≥40 years. A prospective, randomized study is warranted to determine whether retrieval time merits revision for patients of advanced age, as well as the age cutoffs at which such protocols should be applied.