Impact of Maternal Macronutrient Intake on Large for Gestational Age Neonates’ Risk Among Women with Gestational Diabetes Mellitus: Results from the Greek BORN2020 Cohort

Background/Objectives: The effect of maternal macronutrient composition on the risk of large for gestational age (LGA) neonates among women with gestational diabetes mellitus (GDM) is not well understood. This study aimed to investigate these associations in a pregnant cohort in Northern Greece, considering both pre-pregnancy and early pregnancy dietary intake, and stratifying women by pre-pregnancy body mass index (BMI). Methods: From a total of 797 eligible pregnant women, the 117 (14.7%) who developed GDM (and thus were included in the study) completed the validated Food Frequency Questionnaires (FFQs). Macronutrient intake was assessed for the six months before pregnancy and until mid-gestation, prior to the oral glucose tolerance test. Data were compared with European Food Safety Authority (EFSA) guidelines, and participants were stratified by pre-pregnancy BMI (normal vs. overweight/obese). Multivariate logistic regression was used to estimate adjusted odds ratios (aORs) for LGA risk. Results: In normal-BMI women with GDM, higher dietary fiber (aOR = 1.39) and vegetable protein (aOR = 1.61) intake before pregnancy were both significantly associated with an increased risk of LGA. During early pregnancy, the elevated risk from vegetable protein persisted (aOR = 1.51). Among overweight/obese women, no significant pre-pregnancy associations were observed. However, during early pregnancy, a higher percentage of total carbohydrate intake was linked to increased LGA risk (aOR = 1.11), while maintaining saturated fatty acids “as low as possible” reduced the odds of LGA (aOR = 0.71). Elevated vegetable protein intake also increased LGA risk (aOR = 1.61). Conclusions: Maternal macronutrient intake prior to and during early pregnancy may influence LGA risk in GDM, with distinct patterns according to pre-pregnancy BMI. These findings underscore the importance of tailoring dietary recommendations—especially regarding fiber, vegetable protein, carbohydrates, and saturated fat—to mitigate the risk of LGA in women with GDM.