Impact of elevated peak serum estradiol levels during controlled ovarian hyperstimulation on the birth weight of term singletons from fresh IVF-ET cycles.

Purpose: To investigate the impact of elevated serum estradiol (E2) levels on the day of hCG trigger on the birth weight of term singletons after fresh In Vitro Fertilization (IVF)-Embryo Transfer (ET) cycles.
Methods: Retrospective cohort study of all patients initiating fresh IVF-ET cycles resulting in live births between January 2004 and February 2013. The incidence of low birthweight (LBW) term singletons in patients with E2 levels on day of hCG trigger above or below the 95 % cutoff for E2 values in our clinic (3,069.2 pg/mL) was estimated. Multiple gestations and vanishing twin pregnancies were excluded.
Results: Two thousand nine hundred thirty-nine singleton live births were identified for inclusion. One hundred forty seven (5 %) and 2792 (95 %) live singleton births occurred in patients with peak E2 levels above and below 3,069.2 pg/mL, respectively. The overall incidence of term LBW was 5.4 % in the >3,069.2 pg/mL group compared to 2.4 % in the ≤3,069.2 pg/mL group (P = .038). An E2 level >3,069.2 pg/mL on the day of hCG administration was associated with increased odds of LBW term singletons (OR = 2.29; 95 % CI = 1.03-5.11). The increased odds remained unchanged when adjusting for maternal age (aOR = 2.29; 95 % CI = 1.02-5.14; P = .037), gestational age at delivery (aOR = 2.04; 95 % CI = 1.22-3.98; P = .025), and day 3 versus blastocyst transfer (aOR = 2.5; 95 % CI = 1.11-5.64; P = .023).
Conclusions: Peak E2 level >3,069.2 pg/mL is associated with increased odds of LBW term singletons after fresh IVF-ET cycles. Conservative stimulation protocols aiming not to exceed an E2 level of 3,000 pg/mL may be advantageous for placentation and fetal growth if a fresh transfer is planned.