Association Between Progesterone Level on Trigger Day to Basal Progesterone Ratio and in vitro Fertilization-Embryo Transfer Outcomes in Antagonist Protocols.

Objective: To investigate the relationship between the progesterone level on trigger day (P_trigger) to basal progesterone (bP) ratio and the outcomes of in vitro fertilization-embryo transfer (IVF-ET).

Methods: A retrospective analysis was conducted on women who received an antagonist protocol, with a P_trigger less than 1.5 ng/mL and who underwent fresh embryo transfer. Based on the P_trigger/bP ratio, participants were categorized into four groups: group A (P_trigger/bP < 1, n = 284), group B (P_trigger/bP ≥ 1 and < 2, n = 363), group C (P_trigger/bP ≥ 2 and < 3, n = 165), and group D (P_trigger/bP ≥ 3, n = 118). Recombinant follicle-stimulating hormone was used to stimulate ovulation. Receiver operating characteristic curve analysis was used to analyze the accuracy of the P_trigger/bP ratio in predicting clinical pregnancy following fresh embryo transfer.

Results: A decreasing trend in bP levels was observed across groups (A > B > C > D), while P_trigger levels showed an increasing trend (A < B < C < D). Groups A and B included significantly younger women and required lower doses of gonadotropin (Gn) compared to Groups C and D. The embryo implantation and clinical pregnancy rates in Group A were 34.93% and 49.30%, respectively, significantly higher than those in Group D (23.19% and 33.90%, respectively). After propensity score matching for age, the differences in implantation and clinical pregnancy rates were not statistically significant between Group A and D. The P_trigger/bP ratio had limited accuracy in predicting clinical pregnancy, with an area under the curve of 0.538 (95% CI [confidence interval]: 0.501-0.575, P = 0.044).

Conclusion: A P_trigger/bP ratio of less than 1 was associated with relatively favorable pregnancy outcomes in women undergoing IVF-ET with an antagonist protocol for ovulation induction.