Associations between the Planetary Health Diet in Late Pregnancy and Pregnancy Outcomes in Women with a Raised BMI: Insights from the PEARS study

Background Diet quality in pregnancy is a modifiable factor with important implications for maternal and neonatal outcomes. The Planetary Health Diet (PHD), designed to promote both human health and environmental sustainability, has not been comprehensively evaluated in high-risk obstetric populations. Objective This study aimed to examine the PHD in a pregnant cohort with a raised BMI and its associations with pregnancy outcomes, hypothesising that greater adherence is associated with more favourable pregnancy outcomes. Methods This was a secondary analysis of data from the PEARS study. Pregnant women (n=319) with a BMI ≥25 kg/m 2 and ≤39.9 kg/m 2 in early pregnancy were included in the analysis and the cohort was dichotomised into ‘Low' (≤92.9) and ‘High' (>92.9) PHD Index (PHDI) groups based on the median score in late pregnancy (∼28 week's gestation). Differences in pregnancy outcomes between the ‘High' and ‘Low' groups were explored, with results adjusted for multiple testing. Results In adjusted models, a ‘High' PHDI score was associated with a lower odds of preeclampsia and/or pregnancy-induced hypertension (adjusted odds ratio (OR), 0.21; 95% confidence interval (CI), 0.06-0.68, p=0.01), and a higher likelihood to initiate breastfeeding postpartum (adjusted OR 1.84; 95% CI, 1.04-3.24, p=0.04). In the adjusted model, those in the ‘High' PHDI group had a lower risk of delivering an infant born small for gestational age (birthweight <10 th centile) (OR 0.31; 95% CI, 0.10-1.93, p=0.04). Conclusion This diet may be associated with a lower odds of hypertensive outcomes among pregnant women with a raised BMI, while promoting more sustainable food choices. Greater adherence to the Planetary Health Diet was also associated with a lower risk of delivering a baby born small for gestational age and higher breastfeeding initiation rates, highlighting its potential benefits beyond pregnancy.