Does Serum Estradiol Prior to Progesterone Administration in Programmed Frozen Embryo Transfer Cycle Impacts Live Birth Rate: A Prospective Cohort Study.

Background: There is a paucity of data on the optimal threshold of oestradiol (E2) levels required for successful implantation as this is a valid question to be answered, considering that significant number of in vitro fertilisation cycles are deferred for FET cycles.

Aim: The aim of this study is to investigate the serum E2 levels before starting exogenous progesterone in artificial autologous frozen thawed embryo transfers on pregnancy outcomes.

Settings and design: This was a cohort study wherein clinical data of 213 artificial autologous programmed hormone-regulated frozen embryo transfer (HR-FET) cycles were collected.

Materials and methods: The HR-FET cycles were divided into three groups based on the E2 levels before starting progesterone: Group A: E2 ≤300 pg/mL, Group B: E2 301-500 pg/mL and Group C: E2 >500 pg/mL. After adequate endometrial stripe was appreciated by transvaginal ultrasonography, single blastocyst transfer was performed in all the cycles.

Statistical analysis used and results: The clinical pregnancy rate (CPR) in Groups A, B and C were 41.8%, 73.5% and 0.95%, respectively (P = 0.0001). The live birth rate (LBR) in Groups A, B and C was 18.1%, 62.2% and 0%, respectively (P = 0.0001). The miscarriage rate (MR) was significantly lower (15.3%) when E2 was between 301 and 500 pg/mL (P = 0.001). At both the extremes of serum E2 values, the rate of miscarriage increased. If serum E2 levels were ≤300 pg/mL or >500 pg/mL, the rate of miscarriage was 56.5% and 100%, respectively.

Conclusion: Serum E2 levels in the range of 301-500 pg/mL before starting progesterone in programmed FET cycle are associated with an improved CPR and LBR and also decreased MR as compared to the extreme values of E2 ≤300 pg/mL or >500 pg/mL.