Charting the Maternal and Infant Microbiome: What Is the Role of Diabetes and Obesity in Pregnancy?

Purpose of Review: The purpose of this review is to summarize the evidence on whether diabetes, obesity, and related metabolic derangements during pregnancy are associated with the maternal and infant microbiomes, and to identify gaps in the literature and offer guidance on future research on this topic. Recent Findings: We found circumstantial evidence from four observational studies that the maternal gut microbiome was associated with either pre-pregnancy body mass index, gestational weight gain, gestational diabetes, and/or related metabolic biomarkers in pregnancy; we did not identify any studies that examined whether the vaginal microbiome varied according to these metabolic parameters. Maternal diabetes (in one study) and pregnancy weight status (in three studies) were found to be associated with the infant offspring gut microbiome, although some associations only appeared in certain cohort strata. Patterns of association across both maternal and infant microbiome studies, however, lacked consistency, which may owe to biologic or technical differences, or to the lack of control for important confounders or effect modifiers (e.g., delivery mode in infant microbiome studies). Summary: Metabolic diseases in pregnancy, such as diabetes and obesity, may be associated with the maternal and infant microbiomes, but there is a need for large prospective studies of mother-child dyads from diverse racial and ethnic backgrounds to determine the direction and potential causal nature of these associations. These studies should include serially collected biospecimens, standardized workflows that conserve microbial DNA and RNA, and rich data on clinical outcomes and environmental, lifestyle, and genetic risk factors for obesity and diabetes.