Gestational Diabetes, the Human Milk Metabolome, and Infant Growth and Adiposity.

Importance: Gestational diabetes (GD) is linked to health risks for the birthing parent and infant. The outcomes of GD on human milk composition are mostly unknown. Objective: To determine associations between GD, the human milk metabolome, and infant growth and body composition. Design, Setting, and Participants: Cohort study using data from the Mothers and Infants Linked for Healthy Growth and the Maternal Milk, Metabolism, and the Microbiome studies at the University of Oklahoma and University of Minnesota, large prospective US cohorts with a high proportion of exclusive breastfeeding. Participants were mother-infant dyads recruited between October 2014 and August 2019 who planned to exclusively breastfeed for 3 or more months. Data were analyzed from July 2022 to August 2024. Exposure: GD diagnosed via oral glucose tolerance test. Main Outcomes and Measures: The milk metabolome was assessed by untargeted liquid chromatography-gas chromatography-mass spectrometry at 1 month post partum. Infant growth (weight for length z score, length for age z score, and rapid weight gain) and body composition (percentage body fat and fat-free mass index) from 0 to 6 months were assessed. Linear regression analyses tested associations between GD and milk metabolites, with adjustment for covariates and potential confounders. Results: Among 348 dyads (53 with GD), 27 (51%) of the GD-exposed infants were female and 157 (53%) of nonexposed infants were male; 10 (19%) were Asian, 2 (4%) were Black or African American, and 37 (70%) were White. The mean (SD) age was higher in the GD group (with GD, 34.0 [4.3] years; without GD, 30.7 [4.1] years). In adjusted models, GD was associated with differential levels of 9 metabolites of 458 tested (FDR<0.05); 3 were higher (2-hydroxybutyric acid, 3-methylphenylacetic acid, and pregnanolone sulfate) and 6 were lower in women with GD (4-cresyl sulfate, cresol, glycine, P-cresol sulfate, phenylacetic acid, and stearoylcarnitine). Phenylacetic acid was associated with length for age z score (β = 0.27; SE, 0.13; 95% CI, 0.02 to 0.16), 2-hydroxybutryic acid with percentage body fat (β = -1.50; SE, 0.66; 95% CI, -2.79 to -4.82), and stearoylcarnitine with greater odds of rapid weight gain (odds ratio, 1.66; 95% CI, 1.23 to 2.25). GD was associated with greater length for age z scores (β = 0.48; SE, 0.22; 95% CI, 0.04 to 0.91). Conclusions and Relevance: In this observational cohort study, GD was associated with altered concentrations of several human milk metabolites. The associations between these metabolites and infant growth suggest that milk compositional differences in mothers with GD may beneficially moderate the growth and body composition of their infants.