Prolonging oocyte in vitro culture and handling time does not compensate for a shorter interval from human chorionic gonadotropin administration to oocyte pickup

Objective: To assess the impact of oocyte aspiration, denudation, and sperm injection timing in relation to oocyte hCG exposure time on intracytoplasmic sperm injection (ICSI) outcome.

Design: Cohort study.

Setting: Tertiary medical center.

Patient(s): A total of 614 consecutive ICSI cycles were performed in 421 patients aged <38 years with at least three aspirated oocytes and no more than three previous treatments.

Intervention(s): Gonadotropin-releasing hormone agonist or GnRH antagonist suppression; oocyte pickup (OPU)-hCG interval more/less than 36 hours; OPU-denudation interval more/less than 2 hours; denudation-ICSI interval more/less than 1 hour.

Main outcome measure(s): Fertilization, embryo transfer, and pregnancy rates.

Result(s): Late OPU was associated with more available embryos than early OPU and significantly higher rates of fertilization (66.0% ± 22.8% vs. 61.8% ± 24.3%), ET (99.5% vs. 96.2%), and pregnancy (47.2% vs. 35.4%). This advantage was more pronounced in GnRH agonist cycles. The length of incubation before or after denudation had no effect, regardless of OPU timing. On logistic stepwise regression, OPU timing was the only significant independent predictor of pregnancy (odds ratio 1.6, 95% confidence interval 1.17-2.29).

Conclusion(s): The timing of OPU has a predominant effect on ICSI success, especially in GnRH agonist cycles. Delaying oocyte denudation or sperm injection does not compensate for insufficient postpriming exposure to the follicular environment.