Omega Fatty Acid and Protein Profiles of Colostrum and Transitional Milk in Mexican Women With and Without Gestational Diabetes: A Cross-Sectional Study

Background/Objectives: Gestational Diabetes Mellitus (GDM) involves metabolic alterations that may affect breast milk composition. Imbalances in protein and fatty acid (FA) profiles have been reported in mature milk from mothers with GDM. However, evidence for colostrum and transitional milk is limited, despite the key role of ω-3 and ω-6 Polyunsaturated fatty acids (PUFAs) in neonatal neurodevelopment. This study compared ω-3 and ω-6 PUFAs and protein concentrations in colostrum and transitional milk from women with and without GDM. Methods: This cross-sectional study was conducted from January 2023 to December 2024. Women aged ≥ 18 years with GDM and non-GDM pregnancies recruited at Hospital General de México “Dr. Eduardo Liceaga” were included. Colostrum and transitional milk samples were collected at 0–5 and 6–14 days postpartum, respectively. To assess whether postpartum time (hours) and maternal group (non-GDM vs. GDM) affected milk volume, an analysis of covariance (ANCOVA) was performed. Differences in milk composition between the GDM and non-GDM groups were assessed using Student’s t test or the Mann–Whitney U test, according to variable distribution. Results: A total of 71 milk samples were analyzed: 51 colostrum samples (25 from women with GDM and 26 from women with non-GDM) and 20 transitional milk samples (10 from women with GDM and 10 from women with non-GDM). A moderate correlation was observed between milk volume and postpartum time, with no significant differences between the GDM and non-GDM groups. Colostrum from women with GDM had lower protein content compared with milk from women with non-GDM (3.8 ± 0.4 vs. 5.2 ± 0.5 g/dL, p = 0.02) and transitional milk (1.4 ± 0.2 vs. 2.2 ± 0.2 g/dL, p = 0.02). Transitional milk from GDM group showed higher total fat (5.7 ± 1.8 vs. 2.0 ± 0.4 g/100 g, p = 0.05) and fat-to-protein ratio (3.9 ± 1.1 vs. 1.0 ± 0.3, p = 0.02), along with an increased ω-6/ω-3 ratio driven by higher linoleic acid and lower α-linolenic acid concentrations. Conclusions: GDM was associated with variations in breast milk protein and FA profiles with a potential negative impact on the newborn’s neurodevelopment.