Exploration of the Vaginal and Gut Microbiome, Dietary Intake, and Metabolomics in African American Women by Body Mass Index and Gestational Weight Gain
Authors: Faucher Mary Ann , Greathouse K. Leigh , Hastings‐Tolsma Marie 
Published: September 2019

Purpose/Aim

Characterize the distal gut and vaginal microbiome, urinary metabolites, and macronutrient, micronutrient, and a healthy eating index (HEI) in African American (AA) women by pre‐pregnancy body mass index (pBMI) including obesity class, and gestational weight gain (GWG).

Research Questions and/or Hypothesis

1) The microbiome and urinary metabolites will differ between pregnant AA women based on pBMI, GWG, and class of obesity. 2) Dietary nutrients, food groups, and the HEI will be different between women who are normal weight versus obese, between class I versus class II/III obesity, and by category of GWG.

Significance/Background

Nonpregnant populations show variations in the microbiome and metabolites based on race/ethnicity, body mass index, and disease. Pre‐pregnancy obesity is most prevalent in AA women which impacts maternal health, GWG, and infant health. Gestational weight gain significantly influences perinatal risks and ideal GWG varies by pBMI. Evidence also supports unique food metabolism and variations in diet during pregnancy in AA women.

Methods

We recruited 25 healthy pregnant AA women, sampled the vaginal and distal gut microbiome, obtained urine specimens, and administered a web‐based Automated Self‐Administered 24‐hour Recall (ASA24, 2016) and the food frequency questionnaire (DHQ II) to assess dietary intake history at baseline. Microbiome samples were analyzed using high throughput sequencing of the V4 region of the 16S rRNA gene. Urine samples were analyzed using targeted Liquid Chromatography Mass Spectroscopy (LC‐MS) to identify metabolites. The HEI was calculated using the Diet*Calc software

Findings

Twenty‐one women provided distal gut and vaginal swabs and 22 women provided urine samples at time‐point 1. Fifteen women provided samples at both time‐points. Gut alpha diversity in non‐obese women increased with GWG (P = .048). Gut beta‐diversity also showed significant differences in obese women by GWG (P = .005). A positive correlation was found between GWG and distal gut Bacteroidetes abundance among obese women and a negative correlation with Firmicutes which reversed in women with class III obesity and low GWG. A significant difference was also found in vaginal taxonomic abundance showing decreased Lactobacillus in obese women and increased Megasphaera in obese women with low GWG. The dietary analysis revealed women with class II/III obesity have the poorest diet quality (HEI) as compared with class I, with the poorest diet quality observed in women with obesity gaining above the Institute of Medicine (IOM) GWG recommendations, though not significantly different. Further, higher distal gut Bacteroidales (Phylum: Bacteroidetes) abundance correlated with higher energy intake from fat among women with GWG below recommendations (P = .0049). At time‐point 1, eight endogenous metabolites distinguished obese from non‐obese women; 28 distinguished by class of obesity (P ≤ .05). At time‐point 2, two metabolites distinguished obese from non‐obese women. When considering obese women in class II/III versus those in class I, 33 metabolites were distinguishing. When examining GWG by class of obesity, obese women who gained below IOM recommendations were differentiated by lower values of 2 phosphatidylcholine compound metabolites (P ≤ .05).

Discussion

Results suggest the distal gut microbiota, urinary metabolites, and dietary composition are significantly influenced by pBMI, class of obesity, and GWG. Abundance of specific taxa in the vagina has implications for risk of infection and appears to be influenced by pBMI. Metabolites, mostly related to inflammation and fatty acid oxidation, were significantly different in the obese group. Specifically, dietary fatty acids are known to alter the distal gut microbiome composition and function in relationship to degree of saturation. Dietary fatty acid composition is a possible target for intervention in AA women who are obese to improve pregnancy outcomes. Overall, this pilot data supports further investigation of the diet‐microbiome‐metabolite relationship to determine ideal GWG in AA women by obesity severity to optimize childbirth outcomes.