Physical Activity During Pregnancy, Dietary Adequacy, and Energy-Dense, Nutrient-Poor Food and Beverage Intake: Associations with Preterm Birth

Background/Objectives: Maternal nutrition and physical activity are modifiable behaviours relevant to pregnancy outcomes, but higher activity may coexist with both favourable and unfavourable dietary patterns. This study examined associations between pregnancy physical activity, individualised fruit–vegetable adequacy, energy-dense, nutrient-poor (EDNP) food and beverage intake, and preterm birth. Methods: This cross-sectional study included 1048 postpartum women with singleton live births recruited consecutively at a tertiary maternity hospital in Romania. Physical activity during the last three months of pregnancy was assessed using the Pregnancy Physical Activity Questionnaire and categorised into quartiles of total MET-hours/week. Dietary intake was assessed using an adapted food frequency questionnaire. Fruit–vegetable adequacy was evaluated against individualised recommendations, and EDNP intake was summarised using a composite score derived from fast food, sweets, chocolate, and sugar-sweetened beverages. Preterm birth was defined as delivery before 37 completed weeks of gestation. Results: Preterm birth occurred in 118 cases (11.3%). Higher physical activity categories showed greater fruit–vegetable intake and adequacy, but also higher EDNP intake. After adjustment for maternal age, pregestational BMI, parity, education, and income, physical activity category remained associated with all modelled dietary outcomes. Category 4 had higher odds of fruit–vegetable adequacy than category 1 (OR 2.24, 95% CI 1.55–3.24). In diet-informed models, category 3 had the lowest odds of preterm birth (OR 0.38, 95% CI 0.21–0.68). Conclusions: Total physical activity during pregnancy was associated with a complex dietary profile rather than a uniformly favourable lifestyle pattern. The lowest odds of preterm birth were observed in the third activity category, suggesting a non-linear association.