Clinical outcomes in oocyte donation cycles: GnRH-antagonists versus progesterone-primed ovarian stimulation with micronized progesterone.

Objective: In oocyte donation cycles, does the use of oral natural micronized progesterone (NMP) result in comparable clinical outcomes, compared with gonadotrophin releasing hormone (GnRH) antagonist treatment?

Methods: Retrospective analysis of 1368 oocyte donation cycles (January 2018 to December 2022), and laboratory (n = 793) and clinical outcomes (n = 645) in matched recipients. Donors initiated ovarian stimulation in early follicular phase. To prevent a premature LH peak, the study group received natural micronized progesterone orally concurrently with FSH administration, whereas the control group began GnRH antagonist treatment in a flexible protocol. Live birth rate was the primary outcome.

Results: Duration of stimulation and total gonadotrophins dose were comparable between groups. The NMP group yielded significantly higher retrieved oocytes (15.9 ± 8.5 versus 13.1 ± 7.9; P < 0.001) and mature oocytes (12.8 ± 7.3 versus 11.7 ± 7.3; P = 0.003), and a lower maturation rate (80.89 ± 16.78% versus 89.49 ± 14.48%; P < 0.001). These donors had higher fertilization rates (81.3% versus 74.3%; P < 0.001) and number of usable embryos (4.6 ± 2.0 versus 4.1 ± 2.0; P < 0.001) compared with those treated with a GnRH antagonist. In matched recipients undergoing fresh embryo transfer, reproductive outcomes, including live birth rates, were similar in the GnRH antagonist and NMP groups (47.2% and 44.6%).

Conclusions: Comparable live birth rates were found in fresh embryo transfers for recipients across both groups. The NMP protocol was associated with a higher number of mature oocytes but lower oocyte maturation rate, higher fertilization rates and number of usable blastocysts. Progesterone priming may positively influence oocyte donation cycles.