Maternal Macronutrient Intake and Associated Risk for Gestational Diabetes Mellitus: Results from the BORN2020 Study

<b>Background/Objectives:</b> Limited evidence links maternal macronutrient intake to gestational diabetes mellitus (GDM) risk. Therefore, we evaluated these intakes both before and during pregnancy, comparing macronutrient data against the European Food and Safety Authorities' (EFSA) Dietary Reference Values (DRVs). <b>Methods:</b> Data were prospectively collected from the Greek BORN2020 epidemiologic pregnant cohort, which included 797 pregnant women, of whom 14.7% were diagnosed with GDM. A multinomial logistic regression model assessed the association between macronutrient intake and GDM, adjusting for maternal, lifestyle, and pregnancy-related factors. <b>Results:</b> Women with GDM had higher maternal age (34.15 ± 4.48 vs. 32.1 ± 4.89 years), higher pre-pregnancy BMI (median 23.7 vs. 22.7 kg/m²), and were more likely to smoke during mid-gestation (17.95% vs. 8.82%). Pre-pregnancy energy intake exceeding EFSA recommendations was associated with increased GDM risk (aOR = 1.99, 95%CI: 1.37-2.86). During mid-gestation, higher dietary fiber intake (aOR = 1.05, 95%CI: 1.00-1.10), higher protein intake (aOR = 1.02, 95% CI: 1.00-1.04), and higher protein percentage of energy intake (aOR = 1.08, 95%CI: 1.01-1.17) were all significantly associated with increased GDM risk. Changes from pre-pregnancy to pregnancy showed significant increases in dietary fiber intake (aOR = 1.07, 95%CI: 1.04-1.10), protein (aOR = 1.00, 95%CI: 1.00-1.01), fat (aOR = 1.00, 95%CI: 1.00-1.01), vegetable protein (aOR = 1.01, 95%CI: 1.00-1.03), animal protein (aOR = 1.00, 95%CI: 1.00-1.01), and monounsaturated fatty acid (MUFA) intake (aOR = 1.01, 95%CI: 1.00-1.02), all of which were associated with increased GDM risk. <b>Conclusions:</b> Energy intake above upper levels set by EFSA, as well as increased protein, MUFA, and fiber intake, although beneficial in balanced intakes, may negatively affect gestation by increasing GDM likelihood when consumed beyond requirements.