Early Fetal Growth Trajectories in Gestational Diabetes Mellitus Pregnancies and Large for Gestational Age at Birth

Introduction: Our aim was to examine the fetal growth trajectories in gestational diabetes mellitus pregnancies, from before the GDM diagnosis is made, and to compare it in fetuses destined to be born large for gestational age (LGA)compared to appropriately for gestational age(AGA).

Methods: A retrospective cohort study of multiparous women with a first diagnosis of GDM between 2010-2017.Inclusion criteria -documented midtrimester fetal anatomic survey 18-23weeks prior GDM scan and, additionally,3 consecutive ultrasonic growth assessments following GDM diagnosis. All biometry and percentiles were calculated based on Hadlock-3formula.General linear model was conducted to evaluate fetal growth comparing growth patterns of fetuses destined to be LGA (defined as more than 90th percentile for gestational age).

Results: 313 women with fetal growth measurements at 20.1±1.4, 30.0±2.0, 32.8±2.1 and 35.3±2.1 weeks of gestation, were eligible for analysis.Of them, 61 (11.3%) were diagnosed with LGA at birth.Mean maternal age, ethnicity, prior history of GDM, gestational age at GDM diagnosis and gestational age at delivery were similar between women with LGA neonates and those with AGA neonates. Women with LGA neonates had higher pre-pregnancy BMI (28.3±6.5 vs. 26.3±5.7 kg/m2; p<0.001).A significant time effect was seen for fetuses destined to be LGA with a higher effect size in this group for abdominal circumference (AC) percentile, estimated fetal weight (EFW) percentile and head circumference (HC) to AC ratio Figure1)Within-subject analysis revealed that only the preGDM scan significantly differed from the post-GDM growth scans in the LGA group, whereas no differences were seen for the AGA group.In contrast, for the HC/AC ratio, each pairwise was significantly different in both groups Figure1

Conclusion: In GDM pregnancies, fetuses destined to be LGA at birth present a distinct growth pattern even before GDM diagnosis is made. The growth velocity is more prominent between midtrimester scan and first growth assessment following GDM diagnosis, with only subtle changes thereafter.