Perinatal outcomes in children born after fresh or frozen embryo transfer: a Catalan cohort study based on 14,262 newborns

Abstract

To ascertain whether perinatal outcomes are affected by vitrification and/or controlled ovarian hyperstimulation (COH). Register-based cohort study. Not applicable. Women undergoing invitro fertilization (IVF) between 2008 and 2012 using autologous or donated eggs who had a singleton pregnancy delivered from the 24th week onward. Fresh embryo transfer (ET) or frozen-thawed ET in women undergoing IVF. Primary outcome birthweight, and secondary outcomes gestational age at delivery, small for gestational age, mode of delivery, and perinatal mortality. In the autologous egg population, newborns from the fresh ET group had lower birthweight than the frozen-thawed ET group (3,152.9 ± 545.5g and 3,343.2 ± 532.3g, respectively), and this difference persisted even after adjusting for confounding factors, and the newborns had a higher risk of being small for gestational age (SGA). In contrast, among egg-donor recipients undergoing ET, the mean birthweight did not differ between the groups (3,165 ± 604.15g and 3,143.60 ± 604.21g in the fresh and frozen-thawed ET groups, respectively); however, in the adjusted regression model birthweight was statistically significantly higher in the fresh ET group than the frozen-thawed ET group. The risk of SGA remained comparable between the fresh versus frozen-thawed ET groups. We observed no statistically significant differences in perinatal mortality between groups either in the autologous egg population or in the donor recipient group. Perinatal outcomes are negatively affected by COH and not affected by the vitrification process.