We aimed to investigate the optimal number of oocytes retrieved in normal responders with the gonadotropin-releasing hormone (GnRH) antagonist (GnRHant) protocol in comparison with the GnRH agonist (GnRHa) long protocol. This retrospective study is based on a single-center cohort including 657 fresh cycles with day 3 embryo transfer using the GnRHa long protocol and the GnRHant flexible protocol at the fertility clinic of a university hospital between 2005 and 2019. The rate ratios (RR) of clinical pregnancy were evaluated using log-binomial regression depending on the categories by the number of retrieved oocytes and pituitary suppression methods. After controlling for age, body mass index, and basal follicle-stimulating hormone, women with 10-11 oocytes retrieved demonstrated a significantly higher chance of clinical pregnancy compared to the reference group (4-5 oocytes) (RR 1.68, 95% CI 1.12-2.53). However, retrieval of more than 11 oocytes did not show a significant difference in pregnancy rates (PR) from the reference group. In women treated with GnRHant, a significantly higher clinical PR was also observed in women with 10-11 oocytes retrieved compared to the reference group (RR 1.90, 95% CI 1.05-3.42). In women treated with GnRHa long protocol, a higher probability of clinical pregnancy was observed (RR 1.30, 95% CI 0.98-1.73) in the group with 8-11 oocytes retrieved and it demonstrated borderline statistical significance (P = 0.07). In summary, the optimal number of oocytes for maximizing the rate of a clinical pregnancy is different according to the method of pituitary suppression. Too many oocytes do not seem to be beneficial for achieving better clinical outcomes.
Optimal Oocyte Number in Controlled Ovarian Stimulation with Gonadotropin-Releasing Hormone Agonist/Antagonist and Day 3 Fresh Embryo Transfer.