Dietary Sugar and Saturated Fat Consumption Associated with the Gastrointestinal Microbiome during Pregnancy

Background: Growing evidence supports changes in the gastrointestinal microbiome over the course of pregnancy may have an impact on the short- and long-term health of both the mother and the child.

Objective: Our objective was to explore the association of diet quality, as measured by the Healthy Eating Index (HEI), with the composition and gene ontology (GO) representation of microbial function in the maternal gastrointestinal microbiome during pregnancy.

Methods: We conducted a retrospective, observational analysis of n = 185 pregnant participants in the Pregnancy Eating Attributes Study. Maternal dietary intake was assessed in the first trimester using the automated self-administered 24-h recall method, from which the HEI 2015 was calculated. Rectal swabs were obtained in the second trimester and sequenced using the NovaSeq 6000 system shotgun platform. We used unsupervised clustering to identify microbial enterotypes representative of maternal taxa and GO functional term composition. Multivariable linear models were used to identify associations between taxa, functional terms, and food components while controlling for relevant covariates. Multinomial regression was then used to predict enterotype membership based on a participant's HEI food component score.

Results: Those in the high diet quality tertile had a lower early pregnancy BMI [mean (M) = 23.48 kg/m², SD = 3.38] compared with the middle (M = 27.35, SD = 6.01) and low (M = 27.49, SD = 6.99) diet quality tertiles (P < 0.01). There were no statistically significant associations between the HEI components or the total HEI score and the 4 alpha diversity measures. Differences in taxa and GO term enterotypes were found in participants with, but not limited to, a higher saturated fat component score (β = 1.35, P = 0.01), added sugar HEI component (β = 0.07, P < 0.001), and higher total dairy score (β = 1.58, P = 0.01).

Conclusions: Specific dietary components are associated with microbial composition and function in the second trimester of pregnancy. These findings provide a foundation for future testable hypotheses.