Supraphysiological estradiol levels on the hCG trigger day are associated with SGA for singletons born from fresh embryo transfer

The effects of supraphysiological estradiol (E-2) on neonatal outcomes and the significance of specific E-2 concentrations remain unclear. The purpose of this study was to investigate whether supraphysiological E-2 levels on the human chorionic gonadotropin (hCG) trigger day are associated with small size for gestational age (SGA) in singletons born from fresh embryo transfer (ET) cycles. Patients with singleton pregnancies who delivered after the transfer of fresh embryos, during the period from July 2012 to December 2017, at our center were included. We excluded cycles involving a vanishing twin, maternal age >35 years, basal follicle-stimulating hormone >= 10 mIU/ml, or anti-Mullerian hormone <= 1 ng/ml. We then divided all cycles into five groups by E-2 level on trigger day: group A, <2000 pg/ml (reference group); group B, 2000 pg/ml <= E-2<2999 pg/ml; group C, 3000 pg/ml <= E-2<3999 pg/ml; group D, 4000 pg/ml <= E-2<4999 pg/ml; and group E, >= 5000 pg/ml. The prevalence of SGA among singletons from fresh ET was the primary outcome. The SGA rate significantly increased when the E-2 level was >= 4000 pg/ml, as observed by comparing groups D (odds ratio [OR]: 1 center dot 79, 95% confidence interval [CI]: 1 center dot 16-2 center dot 76, P = 0 center dot 01) and E (OR: 1 center dot 68, 95% CI: 1 center dot 10-2 center dot 56, P = 0 center dot 02) with the reference group. Multivariate logistic regression indicated that a serum E-2 level of at least 4000 pg/ml on the hCG trigger day was associated with increased SGA and with significant differences for groups D (adjusted OR [AOR]: 1 center dot 65, 95% CI: 1 center dot 05-2 center dot 59, P = 0 center dot 03) and E (AOR: 1 center dot 60, 95% CI: 1 center dot 03-2 center dot 53, P = 0 center dot 04) relative to the reference group. In conclusion, in fresh ET cycles, the supraphysiological E-2 >= 4000 pg/ml on the hCG trigger day increases the risk of SGA.

Automated summary

In fresh embryo transfer cycles, it was found that supraphysiological E-2 levels exceeding 4000 pg/ml on the hCG trigger day increase the risk of small size for gestational age (SGA) in singletons.