How low is too low? Cycle day 28 estradiol levels and pregnancy outcomes.

OBJECTIVE

To determine the utility of cycle day 28 estradiol (E2) levels in predicting pregnancy outcomes after IVF.

DESIGN

Retrospective, cohort study.

SETTING

Academic medical center.

PATIENT(S): All IVF cycles resulting in a positive pregnancy test result at our center between January 2007 and December 2012 were included.

INTERVENTION(S): In vitro fertilization with fresh embryo transfer.

MAIN OUTCOME MEASURE(S): A total of 5,471 IVF cycles were identified. Cycles were stratified by day-28 E2 level (pg/mL) into three groups: A: ≤50; B: 51-100; and C: >100. Outcomes measured were live birth, clinical pregnancy, biochemical, ectopic, and spontaneous abortion rates.

RESULT(S): There were 806, 588, and 4,077 IVF pregnancies in groups A, B, and C, respectively. Live birth rates were lower in groups A (15.4%) and B (41.2%) compared with group C (77.4%), representing decreased odds of live birth in patients with E2 levels of ≤50 pg/mL (odd ratio 0.05, 95% confidence interval 0.04-0.07) and in patients with levels of 51-100 pg/mL (odds ratio 0.20, 95% confidence interval 0.17-0.25) compared with patients with levels >100 pg/mL. Rates of biochemical and ectopic pregnancies were higher in groups A (66.5%, 6.20%) and B (30.7%, 3.57%) compared with group C (7.31%, 0.66%). An hCG level <50 mIU/mL was associated with increased odds of a biochemical pregnancy and decreased odds of a live birth.

CONCLUSION(S): Low E2 levels early in IVF pregnancies are associated with poorer pregnancy outcomes. Estradiol can be used alone or in conjunction with hCG levels to predict the odds of a live birth.