Serum progesterone levels greater than 20 ng/dl on day of embryo transfer are associated with lower live birth and higher pregnancy loss rates.

Background: Progesterone (P4) is essential for support of the endometrium and implantation of an embryo in the normal menstrual cycle. In programed frozen embryo transfer cycles using exogenous P4 is necessary, as the endogenous production of P4 requires a functioning corpus luteum that is not present in programed cycles. To date, there is continuing debate about ideal serum estradiol and P4 values in frozen embryo transfer cycles.

Methods: Patients underwent single euploid embryo frozen transfer cycles from 2010 to 2013 at a single large academic center. Patients using donor oocytes and patients with changes in progesterone dose during the cycles in question were excluded. All cycles were programed and intramuscular P4 was used exclusively. Only patients administering the same daily dose of P4 throughout the cycle were included (N = 213 patients). Main outcomes were ongoing pregnancy/live birth rates (OPR/LBR), clinical pregnancy rates (CPR), and spontaneous abortions/biochemical pregnancies. CPR was defined by the presence of a sac on 1st trimester ultrasound. Missed abortions were calculated per pregnancy with a sac. Receiver operator characteristic curves (ROC curves) and chi-squared tests were performed for statistical analysis.

Results: Two groups based on day 19 P4 levels were compared (group A, P4 < 20 ng/ml; group B, P4 > 20 ng/ml). OPR/LBRs were 65 vs. 49 %, group A vs. B, p value = 0.02, RR = 1.33 (1.1-1.7). Missed abortion and biochemical rates were higher in group B as opposed to group A, 27 vs. 12 %, p = 0.01, RR = 0.45(0.24-0.86). When P4 was stratified into five groups based on nanogram per milliliter of progesterone on day 19 (10-15, 15-20, 20-30, 30-40, and >40), there was a trend downward in OPR/LBR (70, 62, 52, 50, and 33 %, respectively). There was also an increase in missed abortion/biochemical rates (7, 15, 27, 32, and 20 %, respectively). Multiple logistic regression showed an increase in OPR/LBR when accounting for age, day 2 FSH, weight, number of embryos biopsied, and number of euploid embryos.

Conclusion: P4 levels >20 ng/ml on the day of transfer (during frozen single euploid embryo transfer cycles) were associated with decreased OPR/LBR.