Optimal Oocyte Number in Controlled Ovarian Stimulation with Gonadotropin-Releasing Hormone Agonist/Antagonist and Day 3 Fresh Embryo Transfer.

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.