Objectives Pregnancy characteristics may influence the infant fecal microbiota during early life. We aimed to examine associations of maternal gestational weight gain with infant fecal microbiota composition, bacterial community richness, and Shannon diversity index. Methods We analyzed data from a prospective cohort study of healthy infants. We collected prenatal data, including report of mother’s gestational weight gain, and infant fecal samples from 84 infant-mother dyads. By applying 16S rRNA gene sequencing and an unbiased clustering by partitioning around medoids using Bray-Curtis distances, we identified four fecal microbiota profiles, and examined the associations of maternal gestational weight gain with the four fecal microbiota profiles, bacterial community richness, and Shannon diversity index. Results Overall, the median age of infants was 4.0 months and 43% were female. The mothers of the 84 infants gained a mean of 14.2 kg (SD, 5.4 kg) during pregnancy. We identified four distinct microbiota profiles: Bifidobacterium-dominant (42%), Enterobacter/Veillonella-dominant (23%), Bacteroides-dominant (19%), and Escherichia-dominant (17%). Infants whose mothers had higher gestational weight gain were less likely to have a Bacteroides-dominant profile, corresponding to a relative risk ratio of 0.83 (95%CI, 0.71–0.96; P=0.01) per 1 kilogram increase in weight. Additionally, higher gestational weight gain was also associated with lower bacterial community richness and Shannon diversity index (P<0.05). Conclusion In this prospective cohort study of healthy infants, maternal gestational weight gain was associated with the infant fecal microbiota profiles, bacterial community richness, and Shannon diversity index.

Results are presented showing a dose-related effect of maternal smoking during pregnancy on cord blood carboxyhemoglobin levels. These elevated cord blood carboxyhemoglobin levels are associated with decreased pH and pO2 levels and raised pCO2 levels. This evidence of chronic intrauterine hypoxia in the infants of mothers who smoke during pregnancy provides a potential mechanism for the reduced birthweight found in these infants.