Relationship between peak serum estradiol levels and treatment outcome in in vitro fertilization cycles after embryo transfer on day 3 or day 5

Objective: To examine the relationships between peak serum estradiol (E₂) levels and treatment outcome in in vitro fertilization (IVF) cycles after embryo transfer (ET) on day 3 or day 5. Design: Retrospective analysis of 697 IVF-ET cycles between January 1999 and December 2001. Setting: A university-affiliated assisted reproduction program. Patient(s): Infertile patients undergoing IVF-ET cycles. Intervention(s): Peak E₂ concentration in serum was determined on the day of human chorionic gonadotropin (hCG) administration. The IVF-generated embryos were cultured for 2 days until transfer on day 3. If more than four 8-cell embryos were present on day 3, embryo culture was continued until day 5 for blastocyst transfer. Main outcome measure(s): Clinical pregnancy rates. Result(s): High peak E₂ levels did not adversely affect treatment outcome. After the cycles were divided according to the day of ET, high peak E₂ levels were associated with improved pregnancy rates after ET on day 5 but not on day 3. Conclusion(s): Increasing peak E₂ levels in IVF cycles are associated with improved pregnancy rates after ET on day 5.