Pet Exposure Is Associated with Altered Gut Microbiota and Higher Phospholipid and Protein Concentrations in the Breast Milk of Overweight/Obese Pregnant Women

Background: The first 1000 days of a child’s life, from a woman’s pregnancy to her child’s second birthday, represent a critical window during which nutritional and environmental exposures shape long-term health. Gut microbiota play an important role in metabolic and overall health. Although pet exposure during pregnancy affects neonatal microbiota, immunity, and development, its effects on maternal health remain unclear. This study investigated the associations of pet exposure with gestational health, maternal and infant microbiota, and breast milk composition in overweight/obese pregnant women. Methods: Fecal samples and breast milk samples were collected from pet-exposed participants (n = 22) and non-exposed controls (n = 32) for 16S rRNA sequencing. Breast milk lipids and proteins were also quantified. Results: Pet exposure before conception, during pregnancy, and postpartum was not associated with gestational diabetes mellitus or gestational weight gain. In the maternal gut, the relative abundances of Proteobacteria, Verrucomicrobia, Sutterellaceae, Enterobacteriaceae, Akkermansia muciniphila, and Parabacteroides were higher, whereas that of Ruminococcus was lower, in the pet-exposed group. In breast milk, the relative abundance of Escherichia-Shigella and the concentrations of phosphatidylinositol 36:2, phosphatidylethanolamine 38:3, lysine, and β-casein were higher, whereas the abundance of Rothia was lower, in the pet-exposed group. The relative abundance of Escherichia-Shigella was also lower in the infant gut of the pet-exposed group. Conclusions: In overweight/obese pregnant women, pet exposure was associated with differences in maternal gut and breast milk microbiota, higher concentrations of selected breast milk phospholipids and β-casein, and lower Escherichia-Shigella abundance in the infant gut.