Is conception by in vitro fertilization associated with altered antenatal and postnatal growth trajectories?

Objective: To study whether the growth trajectory of the first, second, and third trimester, birth, and 5 years of age differs between children born following fresh embryo transfer (fresh ET), frozen−thawed embryo transfer (FET), and children born after natural conception (NC). Design: Historical cohort study of children. The analysis compared cross-sectional and longitudinal differences in measurement between individuals stratified by method of conception. Setting: Not applicable. Patients: Participants were born between 1997 and 2012 by NC (n = 65,683), fresh ET (n = 576), and FET (n = 179). Data were available for method of conception and fetal, maternal, and neonatal characteristics and measurements at 5 years. Intervention (s): None Main Outcome Measure(s): Size at first, second, and third trimester, birth, and 5 years. Result(s): In the longitudinal model, first trimester crown−rump length was significantly longer after fresh ET compared to NC. Second trimester head size was larger after fresh ET and after FET compared to NC. Birth weight was lower after fresh ET conception compared to FET. At 5 years of age, children conceived by fresh ET and FET were no heavier than peers conceived by NC. Conclusion(s): Individuals conceived by in vitro fertilization have significantly different antenatal growth trajectories during the first and second trimester compared to those conceived by NC, and differences persist at birth for weight and head size. The relevance of these different growth trajectories remains uncertain, and larger prospective studies are required.