Does diet quality change from periconception to 3 years postpartum?: findings from a large U.S. cohort.

Little is known about diet quality changes during the transition from periconception to postpartum. We aimed to describe within-person changes in diet quality and related factors from the periconceptional period to 3 years postpartum in a socioeconomically and geographically diverse cohort of U.S. pregnant individuals. We analyzed data from 4,423 participants in the Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be Heart Health Study, followed from 6‒13 weeks of gestation to approximately 3 years postpartum. Usual dietary intake in the 3 months around conception and the 3 months before the postpartum visit were estimated from a food frequency questionnaire. We calculated the proportion of participants meeting food group recommendations from the 2020-2025 Dietary Guidelines for Americans. For each food group, we estimated the proportion of participants with meaningful increases or decreases (defined as an increase or decrease by at least 20% of the recommended intake) in intake density, and determined differences by maternal characteristics. For all food groups, adherence to recommendations was consistently low during both the periconceptional and postpartum periods, with few individuals' diets changing over time. Across food groups, the proportions of participants who improved adherence to recommendations ranged from 4% to 19%, while 7% to 15% of participants experienced declines in adherence. Although few participants met recommendations, meaningful increases were observed in intake densities of vegetables, protein foods, oils, added sugars, and saturated fats (30%-49%), while decreases were common for fruits, grains, dairy, and added sugars (27%-47%). These changes primarily varied according to race and ethnicity, and education. Improving the current food environment and providing sustained, accessible nutritional support that extends into the postpartum period may help individuals of reproductive age meet the Dietary Guidelines, which is crucial for promoting maternal and child health outcomes and reducing related inequities.