Pre-pregnancy body mass index classification and weight gain according to new brazilian protocols and their association with gestational diabetes mellitus

Abstract Objective: This study investigated the association between gestational weight gain based on the new weight gain curve adopted by the Brazilian Ministry of Health for pregnant women and the risk of developing Gestational Diabetes Mellitus (GDM). Methods: Cross-sectional study was conducted with 104 pregnant women—52 with GDM and 52 without—matched for age, self-reported skin color, pre-existing hypertension, and family history of type 2 diabetes. Statistical analyses were performed using SPSS version 19.0. Categorical variables were analyzed using the Chi-square or Fisher's exact test, and continuous variables with the Student's t-test or Mann–Whitney U test. Two multivariate logistic regression models were applied: one using BMI and GWG as continuous variables and another using their categorical classifications. Odds ratios (OR) were calculated as exp(b), and models were adjusted for age, skin color, income, education, and family history of diabetes. A p-value < 0.05 was considered significant. Results: Women with GDM reported less physical activity before (26.9% vs. 46.2% p = 0.042) and during pregnancy (17.3% vs. 40.4% p = 0.009). Regarding pre-gestational nutritional status, women with GDM showed a higher prevalence of overweight (53.9% vs. 30.8%), while obesity was more frequent among women without GDM (40.4% vs. 26.9%), although these differences were not statistically significant (p = 0.059). Women with GDM had lower median gestational weight gain (4.5 kg vs. 8.0 kg, p < 0.001) and a higher proportion exceeded the recommended values (84.6% vs. 40.4%). Excessive GWG was significantly associated with GDM: each additional kilogram gained increased the odds of developing GDM by 28% (aOR 1.28; 95% CI: 1.12–1.47, p < 0.001). Conclusions: Excessive gestational weight gain was significantly associated with GDM, underscoring the importance of monitoring maternal weight gain to prevent complications.