Planetary Health Diet and Risk of Cardiometabolic Diseases Among Women With Gestational Diabetes

Importance The Planetary Health Diet (PHD) integrates health and environmental sustainability, yet its association with chronic disease outcomes remains underexplored, particularly among women with a history of gestational diabetes (GD), who are at elevated risk of type 2 diabetes (T2D) and cardiovascular disease (CVD). Objective To investigate the associations of adherence to the PHD with risks of T2D, CVD, and long-term weight change among women with a history of GD. Design, Setting, and Participants This cohort study used data from the Nurses’ Health Study II. A subset of participants with a history of GD was followed up from June 1991 to June 2021. Data were analyzed from February 1, 2024, to April 9, 2025. Exposures Adherence to the PHD was assessed using the Planetary Health Diet Index (PHDI), which was derived from food frequency questionnaires administered every 4 years. Main Outcomes and Measures Cox proportional hazards regression models were used to assess hazard ratios (HRs) and 95% CIs for the risk of T2D and CVD. Associations between PHDI changes and concurrent 4-year weight changes were evaluated using multivariable marginal models with generalized estimating equations. Results During 120 465 person-years of follow-up among 4633 women with a history of GD (mean SD age, 38.9 6.1 years), 90 incident CVD cases (38 myocardial infarction MI and 52 stroke) and 1053 incident T2D cases were observed. Women in the highest tertile of the PHDI had a 63% lower risk of MI (HR, 0.37; 95% CI, 0.16-0.86; P for trend = .01) compared with those in the lowest tertile, independent of body mass index (BMI) and other covariates. Higher PHDI was also associated with a lower risk of overall CVD and T2D; however, mediation analysis indicated that BMI accounted for 79.6% (95% CI, 16.5%-98.7%; P lt; .001) of the association with T2D and 15.1% (95% CI, 2.8%-52.5%; P = .02) of the association with CVD. Notably, decreasing PHDI was associated with greater weight gain ( P for trend lt; .001), with the group experiencing the largest 4-year decrease in PHDI showing a mean weight gain of 2.3 (95% CI, 2.0-2.6) kg. Conclusions and Relevance In this cohort study of women with a history of GD, higher PHDI was associated with lower risk of myocardial infarction and better weight management. These findings also emphasize the importance of postpartum weight management to reduce the risk of progression from GD to T2D and CVD.