Estradiol level on day 9 as a predictor of risk for ovarian hyperresponse during controlled ovarian hyperstimulation

Purpose: To investigate the estradiol (E₂) level in the mid-follicular phase during controlled ovarian hyperstimulation (COH) and evaluate it as a predictor of a high risk for ovarian hyperresponse.Methods: From January 1996 to October 2001, the records of a total of 146 patients undergoing 164 COH cycles were retrospectively reviewed. All patients received the long protocol of GnRH agonists from the previous mid-luteal phase and then hMG or FSH from day 3 of the menstrual cycle. The E₂ level was evaluated on day 9. Ovarian hyperresponse was defined as 1) an E₂ level on the day of hCG injection was >4000 pg/mL, or 2) the necessity for coasting during COH to decrease the risk of ovarian hyperstimulation syndrome (OHSS).Results: Of the 52 cycles in which day 9 E₂ level was >800 pg/mL, 29 (55.8%) fulfilled the criteria for ovarian hyperresponse. None of patients whose day 9 E₂ level was <300 pg/mL met the criteria for hyperresponse. The pregnancy rate in the groups with day 9 E₂ level <300 pg/mL was 42.9%; for an E₂ level = 300–800 pg/mL, 49.2%; and for an E₂ level >800 pg/mL, 32.7%. The corresponding implantation rates were 18.8, 28.0, and 17.0%. The E₂ level on day 9 did not correlate with clinical pregnancy rates or implantation rates.Conclusions: A high E₂ level in the mid-follicular phase was predictive of patients with a high ovarian response. An E₂ level on day 9 of menstrual cycle of >800 pg/mL suggests an increased risk for ovarian hyperresponse, and appropriate management should be instituted to decrease the risk of OHSS.