Association between objectively measured physical activity and maternal stool microbiota during pregnancy: results from a preliminary investigation

Background This study investigated the relationship between objectively measured physical activity (PA) and gut microbiota composition during pregnancy. Methods In an ongoing birth cohort study, the Fitbit Charge wearable activity monitor was used to objectively measure PA during pregnancy. To profile the composition of gut bacterial microbiota, 16S rRNA sequencing was performed on a third trimester stool sample. Differences in alpha diversity metrics (richness, Pielou’s evenness, and Faith’s phylogenetic diversity) by PA were determined using linear regression, whereas beta diversity (unweighted and weighted UniFrac, Canberra, and Bray-Curtis) relationships were assessed using permutational multivariate analysis of variance (PERMANOVA). Differential abundance testing at both the amplicon sequence variants and genus level was conducted using Analysis of Compositions of Microbiomes with Bias Correction 2; tests were corrected for false discovery rate (FDR) and considered significant if p FDR 0. 05. Results The analytic sample included 68 pregnant women with both PA and 16S rRNA sequencing data (median age quartile 1; quartile 3 = 30. 7 26. 6; 33. 3 years; 56% Black). Women typically took around 5000 steps per day (second trimester median = 5486; third trimester median = 5074) and the majority of activity minutes were classified as sedentary (second trimester median = 77%; third trimester median = 78%). None of the PA variables during the second or third trimester were associated with gut microbiota richness, evenness, or diversity. After covariate adjustment, the proportion sedentary during the second (Weighted UniFrac p = 0. 035, R 2 = 0. 038) and third (Bray-Curtis p = 0. 034, R 2 = 0. 025) trimesters were significantly associated with stool microbiota composition. Additionally, the proportion “fairly” or “very active” during the third trimester was significantly associated with stool microbiota composition (PERMANOVA; Bray-Curtis p = 0. 047, R 2 = 0. 025). These compositional differences were partly characterized by significantly lower abundances of Prevotella and Pasteurellaceae ASVs and higher abundances of Acidaminococcus and Finegoldia in pregnant women with higher second and third trimester sedentary time (p FDR 0. 05). Two specific 16S rRNA sequence variants (ASV₈4 Acidaminococcus intestine and ASV₁34 Oscillospirales sp. ) were also positively associated with sedentary behavior. No significant microbial changes were observed with the proportion of time spent “fairly” or “very active” during the third trimester. Conclusions These findings highlight sedentary behavior as a potential modifiable factor related with maternal gut microbiota composition during pregnancy. This study forms the basis for future studies on the impact of sedentary time on gut microbiota during pregnancy.