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 (E(2)) 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 E(2) 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 E(2) levels did not adversely affect treatment outcome. After the cycles were divided according to the day of ET, high peak E(2) levels were associated with improved pregnancy rates after ET on day 5 but not on day 3. CONCLUSION(S): Increasing peak E(2) levels in IVF cycles are associated with improved pregnancy rates after ET on day 5.