Impact of estrogen-to-oocyte ratio on live birth rate in women undergoing in vitro fertilization and embryo transfer

In order to evaluate whether the ratio of serum estrogen level on the day of human chorionic gonadotrophin (hCG) administration to number of oocyte retrieved has any impact on live birth rate in women undergoing in vitro fertilization (IVF), we retrospectively analyzed the clinical data from 7,112 women treated with GnRH-a long protocol in our center. Cycles were firstly divided into 6 groups according to the E-2/oocyte ratio (< 150 pg/ml; 150 similar to 300 pg/ml; 300 similar to 450 pg/ml; 450-600 pg/ml; 600-750 pg/ml; >= 750 pg/ml). Live birth rate (39.4%) in women with E-2/oocyte ratio >= 750 pg/ml was the lowest compared with that in other groups. We further divided the top 10% of patients into high estrogen group (E-2/oocyte >= 740 pg/ml; n = 713). Compared with controls, those with high E-2/oocyte ratio had significantly higher peak E-2 level (6711.85 pg/ml versus 4670.89 pg/ml; P = 0.000) on the day of hCG administration; however, the live birth rate (39.27% versus 45.67%; P = 0.001) was significantly lower for women with high estrogen level. Thus, we conclude that high E-2/oocyte ratio adversely affects live birth rate in women undergoing IVF treated with GnRH-a long protocol.