The Relationship Between Fiber Intake and Gut Bacterial Diversity and Composition During the Third Trimester of Pregnancy.

BACKGROUND/OBJECTIVES: High fiber (34-36 g/day) diets are recommended during pregnancy due to inverse associations with constipation and adverse pregnancy health outcomes, including pre-eclampsia and gestational diabetes. However, the mechanism for this protective effect is poorly defined. Fiber may be protective due to its impact on the composition and function of specific bacteria within the pregnancy gut microbiome. The purpose of this analysis was to investigate whether a sub-sample of cohort study participants in their third trimester met daily dietary fiber and vegetable intake recommendations and, in turn, how this impacted bacterial composition and butyrate-producing genes within the gut microbiome. METHODS: Pregnant participants (n = 52) provided stool samples and survey data, which were used to calculate fiber and vegetable intake. Genomic DNA was extracted from the stool samples, followed by PCR to amplify the V4 region of the 16S rRNA gene. Amplicons were sequenced and mapped to the RDP reference. Quantitative real-time PCR was used to measure the abundance of bacterial genes for butyrate production. RESULTS: Of the pregnant participants in this sample, 84.7% and 92.3% failed to meet recommendations in the Dietary Guidelines for Americans for dietary fiber and vegetable intake, respectively. All four participants who met the vegetable recommendation were a subset of those who met the fiber recommendation. The participants who met the pregnancy fiber recommendation had gut microbiotas with greater alpha diversity (Shannon and Inverse Simpson) than those who did not. However, there was no association between dietary fiber intake and the abundance of bacterial genes for butyrate production. CONCLUSIONS: This research suggests that general fiber intake during pregnancy has a modest association with the gut bacterial community. These preliminary results demonstrate a need to improve fiber intake during pregnancy. Further, studies that measure the relationship between dietary intake of specific types of fiber and associations with specific gut bacterial community members and their functions are needed.