Premature progesterone elevation spares blastulation but not pregnancy rates in in vitro fertilization with coculture

OBJECTIVE: To clarify whether embryo development to the blastocyst stage may be affected by premature P elevation during controlled ovarian hyperstimulation (COH) for IVF-ET with embryo coculture. DESIGN: Retrospective study. SETTING: Tertiary care infertility center. PATIENT(S): One hundred thirty-one women undergoing 153 IVF-ET cycles with embryo coculture. INTERVENTION(S): Patients underwent COH with GnRH agonist and hMG. Embryos were cocultured up to the blastocyst stage. According to plasma P levels on the day of hCG, two groups were defined: low P (P < or = 0.9 ng/mL; conversion factor to SI unit, 3.180) and high P (P > 0.9 ng/mL). MAIN OUTCOME MEASURE(S): Blastulation (number of blastocysts/number of noncavitating embryos x 100) and pregnancy rates (PRs). RESULT(S): Blastulation rates were similar in the low and high P groups (51% and 48%, respectively). Moreover, patients included in the high P groups achieved significantly lower clinical and ongoing PRs (12% versus 29% and 7% versus 25%, respectively). CONCLUSION(S): The lack of difference in blastulation rates between the groups further supports the hypothesis that premature P elevation does not alter oocyte and embryo quality. Hence, the observed decrease in PRs is likely to reflect impaired endometrial receptivity in the high P group.