Number of Oocytes Retrieved as a Criterion for "freeze-All" Strategy versus a Single "rescue" Bolus of Low-Dose Human Chorionic Gonadotropin Following GnRH Agonist for Ovulation Triggering: A Pilot Study

Aim: To evaluate the number of oocytes retrieved as a criterion - when to use a "freeze-all" or low-dose "rescue human chorionic gonadotropin (hCG)" strategy. Methods: A retrospective study. Instead of the classic hCG trigger, an E2 level of ≥3,000 pg/mL was used to trigger ovulation with GnRH agonist. The decision whether to "freeze all" or perform fresh embryo transfer (ET) with a bolus of hCG was made based on a maximum number of 20 oocytes retrieved. Beyond this cut off, a "freeze-all" strategy was implemented. Below this cut-off value, a fresh ET using a single bolus of 62.5 μg hCG on day 3 following oocyte pick-up was performed. The main outcome measures were clinical pregnancy rates and ovarian hyperstimulation syndrome (OHSS). Results: E₂ and progesterone levels increased after the rescue hCG bolus administration (E₂ from 643.4 ± 311.1 to 1,086.1 ± 574.7 pg/mL, p = 0.003 and progesterone from 13.1 ± 4.8 to 39.2 ± 28.7 ng/mL, p < 0.0001). The clinical pregnancy rates were 25% in the freeze-all group and 32% in the rescue hCG group (p = 0.57). OHSS was not reported in either group. Conclusions: Both strategies seem to be efficacious and safe. An upper limit of 20 retrieved oocytes appears to be safe for applying a rescue hCG strategy.