(P27-016-25) Adherence to the Planetary Health Diet Index and Fetal Body Composition Based on Three-Dimensional Ultrasonography in the Fetal 3D Study – Singletons

Objectives: Suboptimal diet during pregnancy is linked to adverse birth outcomes. In 2019, the EAT-Lancet Commission developed the Planetary Health Diet Index (PHDI), a reference diet promoting a plant-based diet, with moderate amounts of animal-based foods. While epidemiological and mechanistic evidence has demonstrated PHDI’s role in cardiometabolic health in non-pregnant individuals, its suitability during pregnancy remains understudied. Therefore, we examined the associations between PHDI and fetal growth and body composition across pregnancy, among a racially/ethnically diverse, prospective US pregnancy cohort (2009-2013).

Methods: At enrollment (8-13 gestational weeks), pregnant women in the NICHD Fetal Growth Study – Singletons completed a self-administered semi-quantitative,139-item modified version of the Diet History Questionnaire-II. The PHDI total score (range 0-140) and the 14 component scores were calculated using a standardized scoring criteria. Women (n=1464) were categorized into tertiles of PHD adherence (low < 83: n=480, 33%; moderate 83-92: n=491, 34%; high >92: n=493, 33%). We evaluated estimated fetal weight (EFW) and body composition (fractional lean and fat arm volumes - FLAVol and FFAVol, abdominal area - AA, and maximum abdominal subcutaneous tissue thickness - MASCTT), measured in up to five 3D ultrasounds from 15 to 40 weeks’ (w) gestation by certified sonographers. Growth trajectories for all fetal measures were modeled using linear mixed models; weekly mean differences were compared across PHDI adherence tertiles, adjusted for covariates including maternal age and pre-pregnancy BMI.

Results: Fetuses of women with the highest versus lowest PHDI adherence had larger EFW from 32-40w, smaller FLAVol from 34-37w, and larger AA at 25-26w. Fetuses of women with moderate versus lowest PHDI adherence had larger EFW from 32-39w, smaller FLAVol from 34-38w, larger FFAVol from 35-38w, larger AA from 39-40w, and larger MASCTT from 36-38w.

Conclusions: Higher maternal adherence to PHDI was associated with greater fetal weight and adiposity and less lean tissue in the third trimester which could have future metabolic implications for the offspring.

Funding Sources: Supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Health of Child Health and Human Development.