Does the estradiol level on the day of human chorionic gonadotrophin administration have an impact on pregnancy rates in patients treated with rec-FSH/GnRH antagonist?

Abstract

BACKGROUNDThe purpose of this prospective observational study was to evaluate the association between estradiol (E2) levels on the day of human chorionic gonadotrophin (hCG) administration and pregnancy rates in a recombinant FSH (rec-FSH) antagonist fixed protocol.METHODSA group of 207 patients (≤39 years of age), treated by IVF/ICSI, received 200 IU/day rec-FSH from Day 2 of the cycle and daily GnRH antagonist starting on Day 6 of stimulation. The criteria for hCG administration included only the presence of ≥3 follicles of ≥17 mm diameter. One to two embryos were transferred on Day 3 after oocyte retrieval.RESULTSThe area under the curve (AUC) for E2 on the day of hCG could not distinguish between pregnant and non-pregnant women (AUC:0.5; 95 confidence interval (CI): 0.42-0.59). No significant difference was observed between the three percentile groups of E2 values on the day of hCG administration [group 1, lower 25th percentile (<1142 pg/ml); group 2, medium 50th percentile (1142-2446 pg/ml) and group 3, higher 75th percentile (>2446 pg/ml)] for the ongoing pregnancy rates (P = 0.52). On the contrary, the linear regression model showed that higher E2 values on the day of hCG administration significantly improved the scores of transferred embryos (P = 0.01) as well as the total embryo score (P = 0.02). Yet subgroup analysis only in this high responders group revealed lower E2 and progesterone levels on the day of hCG in pregnant women compared with the non-pregnant (P = 0.01).CONCLUSIONSE2 concentrations on the day of hCG administration in GnRH antagonist cycles are not associated with pregnancy rates. A potential deleterious impact of estradiol on endometrial receptivity is shown for the high responders who have high E2 levels and improved embryo quality without a concomitant rise in pregnancy rate.