Adherence to the EAT-Lancet Planetary Health Diet during pregnancy and associations with preterm birth and infant size: a prospective analysis from the New Hampshire Birth Cohort

BACKGROUND: The Planetary Health Diet (PHD), proposed by the EAT-Lancet Commission, seeks to optimize health while preserving the environment. Its benefits for chronic disease prevention are established, but its impacts on birth outcomes are unclear. OBJECTIVES: To assess the association between PHD adherence during pregnancy and newborn outcomes. METHODS: This prospective study included 1431 mother-infant dyads from the New Hampshire Birth Cohort Study. Diet during pregnancy was assessed once at 24-28 wk gestation via a food-frequency questionnaire to calculate the Planetary Health Diet Index (PHDI). Gestational age, birth weight, length, and head circumference were abstracted from medical records. Dietary patterns were identified through self-organizing maps using PHDI components. Associations between PHD and birth outcomes were modeled using multivariable regressions. RESULTS: Highest PHDI tertile participants were older, had lower prepregnancy BMI, were more often nonsmokers, and had higher neighborhood socioeconomic status. In adjusted regression models, 10-unit increase in PHDI was associated with higher birth weight [β = 24.4 g, 95% confidence interval (CI): 1.21, 43.6], longer gestation (β = 0.10 wk; 95% CI: 0.03, 0.17) and reduced odds of being preterm [odds ratio (OR) = 0.86; 95% CI: 0.74, 0.98]. Three distinct dietary patterns were identified: plant-based, saturated fat-rich, and animal/added sugar-rich. Compared with the plant-based profile, the saturated fat-rich profile was associated with shorter gestation and higher odds of low birth weight (OR = 2.54; 95% CI: 1.23, 5.44). The animal/added sugar-rich profile correlated with lower birth weight (β = -82.4 g; 95% CI: -149.2, -15.6) and shorter length (β = -0.46 cm; 95% CI: -0.84, -0.08). Both nonplant-based profiles increased the odds of preterm birth (OR = 1.92 and OR = 1.66, respectively). CONCLUSIONS: Originally proposed for chronic disease prevention and planetary sustainability, higher adherence to the PHD during pregnancy may also benefit birth outcomes, particularly lower odds of preterm birth.