Impact of trimester-specific nutrition counseling on maternal vitamin D status, and perinatal outcomes in India: a quasi-experimental cohort study

Abstract Background Vitamin D deficiency affects more than 90% of Indian pregnant women, yet its isolated impact on perinatal outcomes remains unclear amid multifactorial nutritional challenges. These pose a challenge to achieving SDG 3.2 targets for reducing neonatal mortality. This study evaluated the effects of trimester-specific nutritional counseling on maternal vitamin D status, nutritional practices, and perinatal outcomes in an Indian cohort.​ Methods A quasi-experimental prospective cohort study was conducted among 173 (88 intervention, 85 control) pregnant women (8–14 weeks of gestation) at a tertiary hospital in New Delhi between October 2023 and May 2025. The intervention included individualized counseling on vitamin D-rich foods, protein, lipids, and weight management at 8–14, 24–28, and 32–36 weeks, along with supplementation. Controls received standard care. Outcomes included serum 25(OH)D, nutrient intake, gestational weight gain, birth weight, and mode of delivery. Analyses used t-tests, correlations, and multivariate regression ( p < 0.05, FDR-adjusted).​ Results A total of 173 participants completed the study. Baseline severe vitamin D deficiency improved significantly more in the intervention group than in the control group, with a large effect size (Cohen’s d = 0.97). Protein intake increased, and nutrition knowledge scores improved substantially following the intervention ( p < 0.05). Birth weights were comparable between groups, and no significant association was observed between maternal vitamin D levels and birth weight. Instead, gestational weight gain, protein intake, and caloric intake emerged as significant predictors of low birth weight (OR 0.73–0.995), while vitamin D was not a significant factor. Higher maternal BMI was associated with an increased likelihood of cesarean delivery (OR 0.87, p < 0.05). Conclusion Trimester-specific nutritional counseling improved maternal vitamin D status and dietary practices but was not significantly associated with birthweight. Overall nutritional adequacy, particularly protein intake and gestational weight gain, appeared more closely related to fetal growth. These findings should be interpreted in light of the study design and warrant confirmation in larger studies.