Received November 11, 2020
Accepted May 29, 2021

OBJECTIVE: Demonstrate the non-inferiority of Clinical Pregnancy Rates in Progestin Primed Ovarian Stimulation compared to GnRH Antagonist Protocol when the freeze-all and blastocyst transfer strategy is applied. METHODS: A retrospective study included all IVF cycles performed at Pró-Criar Reproductive Medicine Center, Belo Horizonte, Minas Gerais, Brazil, between May 2018 and May 2019 using a GnRH antagonist analogue or oral progestins to block the LH peak in IVF/intra-cytoplasmic sperm injection (ICSI) cycles for infertility treatment. RESULTS: The primary outcome of our study was Clinical Pregnancy Rate at the first ET (Blastocyst), was 58.4% in the progestin group and 54.9% in the antagonist group (P = 0.735), a finding consistent with most studies published to date using different progestins. The mean number of retrieved oocytes was 11 in the antagonist group and 9 oocytes in the progestin group (P = 0.009). The fertilization rate was 80% for both groups (P= 0.935). The rate of blastocyst formation per cycle was 50% in the antagonist group and 55.6% in the progestin group (P = 0.106). Stimulation lasted a mean of 10 days in the two analysed groups (P = 0.403) and did not vary with patient age in either group. The gonadotropin dose used was higher in the antagonist group (2025 IU) than in the progestin group (1950 IU) (P = 0.057). In addition, the blockade was effective: there was only one case of spontaneous ovulation, which corresponded to less than 1% of the cycles.CONCLUSIONS: PPos is a non-inferiority alternative to the GnRH Antagonist Protocol in patients undergoing ART. An incidence compatible with the 0.34 to 8% risk described in the literature for failure to control the premature LH surge in antagonist protocol cycles.