Parity modulates impact of BMI and Gestational Weight Gain on gut microbiota in human pregnancy

Shifts in the gut microbiome have been implicated in mediating maternal metabolic adaptations to pregnancy. We investigated the impact of pre-pregnancy BMI (pBMI) and gestational weight gain (GWG) on pregnancy-associated remodeling of the maternal gut microbiome and infant colonization, and whether previous pregnancies modulated observed associations. We found that the gut microbiota of participants with higher pBMI changed less over the course of pregnancy in primiparous, but not multiparous participants. This suggests that previous pregnancies may have persistent impacts on maternal microbiotal adaptations to pregnancy. This ecological memory appears to be passed to the next generation, as parity impacted infant microbial composition of first-pass meconium and modulated the impact of maternal GWG on the infant gut microbiome. This work supports a role for the gut microbiome in maternal adaptations to pregnancy and highlights parity as a key consideration for studies of the microbiome in pregnancy and infants.