Effects of dietary glycemic index and glycemic load on blood pressure and hypertensive disorders of pregnancy in women with preexisting diabetes mellitus: findings from a Brazilian cohort study

Objective To investigate whether the glycemic index (GI) and glycemic load (GL) were associated with blood pressure (BP) and hypertensive disorders of pregnancy (HDP) in Brazilian women with previous diabetes mellitus (DM). Methods Prospective cohort study nested within a clinical trial in a public maternity hospital in Brazil (2016–2024). GI and GL were assessed using food frequency questionnaires in the second and third trimesters. Multiple regressions analyzed associations with HDP, systolic BP (SBP), and diastolic BP (DBP). Results Among 120 pregnant women, HDP prevalence was 25%. Chronic hypertension (odds ratio [OR] = 5.82, 95% CI 1.22–27.84) and glycated hemoglobin (OR = 2.64, 95% CI 1.02–6.83) were predictors of HDP. GI and GL were not directly associated with HDP but were associated with third-trimester BP: GL was associated with SBP (β = 0.17; 95% CI 0.07–0.28) and medium/high GI with DBP (β = 11.39; 95% CI 5.34–17.45). Furthermore, second-trimester GI predicted third-trimester HbA1c (β = 0.038; 95% CI 0.009–0.067). Fiber intake was inversely associated with DBP depending on the GI category (β = 1.61; 95% CI 0.02–3.21). Most participants consumed diets with a medium GI and moderate/high GL. Conclusion Dietary GI and GL were associated with BP hemodynamics in the third trimester, even without a direct association with HDP diagnosis. The results highlight the importance of early nutritional monitoring in high-risk prenatal care to improve maternal and perinatal outcomes in pregnant women with previous DM.