Association Between Maternal Obesity and Gestational Diabetes Mellitus With the Human Milk Microbiome: A Systematic Review

Background: Evidence on the beneficial effects of microorganisms in human milk is emerging. Obesity and gestational diabetes mellitus appear to be related to alterations in the maternal gut microbiota and human milk composition. However, knowledge about the influence of maternal obesity and gestational diabetes mellitus on the human milk microbiota remains limited. Research Aim: To summarize and systematically assess the evidence on the influence of obesity and gestational diabetes mellitus on the diversity and/or composition of the human milk microbiota. Method: A systematic review following PRISMA guidelines was conducted. Searches were performed in the MEDLINE, Cochrane Database of Systematic Reviews, Web of Science, and EMBASE, as well as in ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform. The ROBINS-E tool was used to assess the risk of bias. Out of 1,473 studies identified and 24 protocol records, eight studies were selected for final analysis. Results: Exposure to gestational diabetes mellitus and maternal obesity were associated with changes in the human milk microbiota's diversity and/or composition. Lactating women exposed to obesity had a higher prevalence of Staphylococcus and a lower prevalence of Bifidobacterium in their milk. Those exposed to gestational diabetes mellitus had a higher prevalence of Staphylococcus, Gemella , and Prevotella . Findings regarding bacterial phyla prevalence were inconclusive. Conclusion: Based on the findings presented in this systematic review, it is not yet possible to draw definitive conclusions regarding the true influence of maternal obesity and/or gestational diabetes mellitus on the diversity or composition of the human milk microbiota.