Diet Diversity Is Associated with Prepregnancy Body Mass Index but Not the Pregnancy Third-Trimester Gut Microbiota

The prevalence of women entering pregnancy with overweight or obesity is rising in the United States. The dual burden of undernutrition and overweight or obesity can lead to micronutrient deficiencies. Dietary diversity supports micronutrient adequacy and can be assessed using the minimum dietary diversity for women of reproductive age (MDD-W), a food group-based indicator using 24-h dietary recall data. Lower dietary diversity may be associated with lower gut microbiome diversity and overall community composition; however, the relationship during pregnancy is unclear.

This study aimed to 1) describe associations between prepregnancy body mass index (pBMI) and dietary diversity during pregnancy and 2) investigate whether the pregnancy gut microbiota diversity is associated with dietary diversity.

Data were collected from participants in the Michigan Archive for Research on Child Health cohort (n = 132, third trimester). Twenty-four-hour dietary recall data were used to assess dietary diversity according to the MDD-W indicator. A subset (n = 114) provided fecal samples for 16S ribosomal ribonucleic acid gene sequencing.

On the basis of pBMI, 49% of participants had normal weight, 25% had overweight, and 26% had obesity. Parity, income, and marital status differed significantly across pBMI categories. Overall, 20.5% of participants did not meet the minimum dietary diversity (MDD-W score <5). pBMI was inversely correlated with MDD-W scores, with women with obesity having lower dietary diversity than women with normal weight. Consumption of low-nutrient density foods was similar across pBMI categories. Gut microbiome α- and β-diversity were not associated with MDD-W.

Although no associations between the gut microbiota and diet diversity were observed, our results confirm that women with higher pBMI may be at risk of inadequate micronutrient intake. These results emphasize the value of dietary diversity screening and intervention in care for women with higher pBMI, given the well-established role of micronutrients for maternal and fetal health during the third trimester and beyond.