The associations of pre-pregnancy BMI and gestational weight gain with maternal gut microbiota.

Previous studies reporting the association between gut microbiota dysbiosis and maternal obesity were mostly confined at the phylum level or at postpartum period. This study aimed to investigate the dynamic changes in gut microbial communities associated with maternal obesity at different time points of pregnancy. We performed 16S rRNA gene V3-V4 amplicon sequencing on stool samples from 110 women in all three trimesters and 1-month postpartum. Maternal gut microbial communities associated with maternal pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) were explored. The influence of maternal obesity on gut microbiota trajectories was determined based on longitudinal shifts in community clusters across the trimesters. The richness index of alpha diversity decreased with the progression of pregnancy, particularly in women with excessive GWG. The evenness index in 2nd trimester was found inversely associated with GWG. Various taxonomic differences in 1st trimester were associated with excessive GWG, whereas limited taxonomic differences in 2nd and 3rd trimesters were associated with pre-pregnancy BMI or GWG. Meanwhile, the gut microbiota trajectory with especially depleted genus Faecalibacterium in 1st trimester was associated with excessive GWG (adjusted odds ratio 5.7, 95% confidence interval 1.2-28.1). Moreover, the longitudinal abundances of genus Lachnospiraceae ND3007 group across gestations were depleted in women with overweight/obese pre-pregnancy BMI, while genus Bifidobacterium enriched in women with excessive GWG. Our study shows that dysbiosis of the gut microbiota in early pregnancy may have a significant impact on excess GWG. The abundance of the genus Faecalibacterium in 1st trimester may be a potential risk factor. Clinical trial number: NCT03785093 (https://classic.clinicaltrials.gov/ct2/show/NCT03785093).