Effects of Dietary Quality on Vaginal Microbiome Composition Throughout Pregnancy in a Multi-Ethnic Cohort

<b>Background</b>: Vaginal <i>Lactobacillus</i> predominance is associated with improved vaginal health and reduced pregnancy complications. Little is known about how dietary quality may improve vaginal microbial composition or about dietary interventions that may promote <i>Lactobacillus</i> abundance. To understand the host factors affecting vaginal microbiota during pregnancy in a multi-ethnic cohort in Hawai`i. We hypothesize that better diet quality improves vaginal microbial composition, as represented by <i>Lactobacillus</i> abundance and depletion of anaerobic organisms. <b>Methods</b>: We compared comprehensive diet quality, as measured by the Healthy Eating Index-2015 (HEI-2015), to taxonomic classifications of bacteria present within the vagina. Participants of the four predominant ethnic groups in Hawai'i (Japanese, Filipino, Non-Hispanic White and Native Hawaiian) completed Quantitative Food Frequency Questionnaires (QFFQs) and collected vaginal swabs during each trimester. 16s rRNA amplicon sequencing (V2-V9 regions) was performed on vaginal samples. HEI-2015 scores and macro- and micronutrient intake were compared with the predominant species present using the Mann-Whitney-U test, PERMANOVA, and the Pearson correlation coefficient. A mixed-effects logistics regression model was used to predict the depletion of <i>Lactobacillus</i> species while accounting for confounding demographic factors. <b>Results</b>: Matched, longitudinal data for 40 participants demonstrated three predominant <i>Lactobacillus</i> species: <i>L. crispatus, L. iners,</i> and <i>L. gasseri</i>, with another subset of samples with anaerobic abundance. (Primarily, <i>Atopobium vaginae</i>, <i>Prevotella</i>, and <i>Gardnerella vaginalis</i>.) Non-Hispanic White participants had lower amounts of <i>Lactobacillus iners</i> compared to other racial and ethnic groups. HEI scores correlated with the chao index and observed species number primarily in the first trimester (r = 0.25, <i>p</i> < 0.05). Greater carbohydrate intake was associated with a higher abundance of <i>L. crispatus</i>, while lower carbohydrate intake trended towards more <i>L. iners</i> (0.056) and anaerobic species. <b>Conclusions</b>: Increased carbohydrate consumption and improved diet quality may be associated with beneficial vaginal microbial composition in pregnancy.