Composition of the maternal gastrointestinal microbiome as a predictor of neonatal birth weight

Background The biological mechanism by which the maternal gastrointestinal microbiota contributes to fetal growth and neonatal birth weight is currently unknown. The purpose of this study was to explore how the composition of the maternal microbiome in varying pre-gravid body mass index (BMI) groups are associated with neonatal birth weight adjusted for gestational age. Methods Retrospective, cross-sectional metagenomic analysis of bio-banked fecal swab biospecimens ( n = 102) self-collected by participants in the late second trimester of pregnancy. Results Through high-dimensional regression analysis using principal components (PC) of the microbiome, we found that the best performing multivariate model explained 22.9% of the variation in neonatal weight adjusted for gestational age. Pre-gravid BMI ( p = 0.05), PC3 ( p = 0.03), and the interaction of the maternal microbiome with maternal blood glucose on the glucose challenge test ( p = 0.01) were significant predictors of neonatal birth weight after adjusting for potential confounders including maternal antibiotic use during gestation and total gestational weight gain. Conclusions Our results indicate a significant association between the maternal gastrointestinal microbiome in the late second trimester and neonatal birth weight adjusted for gestational age. Moderated by blood glucose at the time of the universal glucose screening, the gastrointestinal microbiome may have a role in the regulation of fetal growth. Impact Maternal blood glucose in the late second trimester significantly moderates the relationship between the maternal gastrointestinal microbiome and neonatal size adjusted for gestational age. Our findings provide preliminary evidence for fetal programming of neonatal birth weight through the maternal gastrointestinal microbiome during pregnancy.