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

Objective: To study whether the growth trajectory between first, second and third trimester, birthand five years of age differs between children born following fresh (fresh ET), frozen (FET) embryo transfer and children naturally conceived (NC).Design: Historical cohort study of children. The analysis compared cross sectional and longitudinaldifferences in measurement between individuals stratified by method of conception.Setting: North East Scotland Patients: Participants were born between 1997-2012 by NC (n=65,683), fresh ET (n=576) and FET (n=179). Data were available for method of conception, fetal, maternal and neonatal characteristics and measurements at five years.Intervention (s): NoneMain Outcome Measure(s): Size at first, second and third trimester, birth and five years.Result(s): In the longitudinal model, first trimester CRL was significantly longer after fresh ET compared to NC (mean difference 0.30 z score [95% confidence interval 0.13, 0.47] p =0.0006). Second trimester head size was larger after fresh ET (mean difference 0.37 [0.21, 0.54] p<0.001) and after FET (mean difference 0.29 [0.04, 0.53] p=0.022) compared to NC. Birth weight was lower after fresh ET conception compared to FET (mean difference 0.25 [0.09, 0.44 p=0.007]). At five years of age, children conceived by fresh ET and FET were no heavier than peers conceived by NC. Conclusion(s): Individuals conceived by IVF have significantly different antenatal growth trajectories during the first and second trimester compared to 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.