Dietary Mapping of Macronutrient Consumption Before Pregnancy Related to Gestational Diabetes Mellitus

<b>Background/Objectives</b>: Gestational diabetes mellitus (GDM) is a common pregnancy complication, and maternal diet before conception may be an important modifiable risk factor. This study aimed to investigate the association between maternal pre-pregnancy energy and macronutrient intake and the risk of GDM. <b>Methods</b>: Data from the BORN2020 cohort in Northern Greece were used. Women were recruited at their first trimester prenatal visit (11-13 weeks of gestation) and provided detailed dietary data via a validated food frequency questionnaire (FFQ), reflecting intake in the six months prior to conception. Weighted Quantile Sum (WQS) regression models were applied to assess the joint effects of food-derived macronutrient mixtures on GDM risk. Analyses were adjusted for parity, maternal age, pre-pregnancy BMI, thyroid disorders, smoking, energy intake, and physical activity. <b>Results</b>: In total, 797 women were included in the analyses. In normal-BMI women, higher pre-pregnancy intake of energy (aOR = 81.16, 95% CI: 4.55-1447.46), total carbohydrates (aOR = 50.66, 95% CI: 3.59-715.04), total fat (aOR = 9.35, 95% CI: 1.17-74.54), and total protein (aOR = 11.06, 95% CI: 1.14-107.09) were significantly associated with increased odds of GDM. The main contributing foods were energy-dense and processed items such as puff pastry, processed meats, potatoes, refined grains, and dairy products. In contrast, dietary fiber, vegetable protein, and animal protein were not significantly associated with GDM risk. Among overweight and obese women, none of the macronutrient or energy mixtures showed significant associations. <b>Conclusions</b>: For women of normal weight, a pre-conception diet high in energy and macronutrients from processed foods is a significant predictor of GDM risk. This association was not found in overweight or obese women, highlighting a critical window for targeted nutritional intervention for normal-weight individuals before pregnancy.