Early Pregnancy Nutritional Adequacy and Subsequent Gestational Diabetes Risk by Body Mass Index: A Prospective Cohort Study of 2227 Korean Women

<b>Background/Objectives:</b> This study evaluated the association between nutrient intake adequacy during early pregnancy and gestational diabetes mellitus (GDM) risk through a prospective cohort study of Korean pregnant women. <b>Methods:</b> A total of 2227 singleton pregnant women were included in this study. Dietary assessment was conducted once during early pregnancy enrollment using the 24 h dietary recall method. The collected dietary data were analyzed using the CAN-Pro Korean food composition database to calculate nutrient-specific intake levels. Nutrient Adequacy Ratio (NAR) for each nutrient and Mean Adequacy Ratio (MAR), which integrates individual NARs, were calculated based on intake levels. GDM diagnosis was determined using oral glucose tolerance test (OGTT) results conducted between 24 and 28 weeks of gestation. Relative risk (RR) for each individual nutrient was calculated, and logistic regression analysis was performed to estimate odds ratios (OR) for GDM risk according to MAR quartiles. <b>Results:</b> Among 2227 participants, 157 women developed GDM. Compared to the highest MAR quartile, women in the lowest quartile showed significantly increased GDM risk (OR = 1.82, 95% CI: 1.10-2.99), with the second lowest quartile demonstrating similarly elevated risk (OR = 1.75, 95% CI: 1.06-2.88). Among individual nutrients, inadequate vitamin D intake was associated with the highest GDM risk (RR = 3.84), followed by insufficient intakes of vitamin K (RR = 1.89), vitamin B₆ (RR = 1.62), niacin (RR = 1.54), and calcium (RR = 1.39). Body mass index-stratified analysis revealed that the association between low nutritional adequacy and GDM risk was particularly pronounced in women with BMI ≥ 25.0 kg/m², showing up to a four-fold increased risk in the lowest adequacy groups. <b>Conclusions</b>: These findings suggest that low overall dietary adequacy and nutritional imbalance during early pregnancy are associated with increased GDM risk. The results underscore the importance of ensuring adequate and balanced nutrition during early pregnancy for GDM prevention.