Maternal fat-soluble vitamin trajectories and infant birth weight in individuals with overweight or obesity.

BACKGROUND

Birth weight is a strong determinant of long-term metabolic health, with both low birth weight and macrosomia linked to increased cardiometabolic risk. Fat-soluble vitamins A, D, and E modulate pathways relevant to fetal growth, however, their trajectories and potential associations with birth weight in pregnant individuals with overweight or obesity remain scarcely characterized.

OBJECTIVE

To examine maternal vitamins A (retinol), D (25(OH)D), and E (α-tocopherol) concentrations during the second and third trimesters of pregnancy and their associations with birth weight, in individuals with pre-pregnancy overweight or obesity.

METHODS

This secondary analysis of the Exercise Training in Pregnancy Trial (ETIP) study included 57 mother-infant pairs with available vitamin measurements in the second and third trimesters. Plasma retinol and α-tocopherol were measured by high performance liquid chromatography, and serum 25(OH)D by liquid chromatography-tandem mass spectrometry. Birth weight was classified as normal (2500 - < 4000 g) or macrosomic (≥ 4000 g). Circulating vitamin concentrations between trimesters were compared using the Wilcoxon signed-rank test and associations between vitamins and birth weight were examined using multivariate linear regression models.

RESULTS

From the second to the third trimester, mean maternal retinol and 25(OH)D concentrations declined significantly (retinol: 1.52 (SD = 0.37) to 1.32 (SD = 0.33) µmol/L; 25(OH)D: 73.7 (SD = 30.0) to 63.3 (SD = 25.0) nmol/L), whereas α-tocopherol increased from 34.6 (SD = 7.1) to 46.3 (SD = 10.0) µmol/L. In the third trimester, 19.3% had vitamin A insufficiency, while vitamin D deficiency and insufficiency affected 31.6% and 33.3%, respectively. Macrosomia occurred in 43.9% of infants and 56.1% had birth weight within the normal range. Maternal vitamins A, D, and E were not associated with birth weight, and no vitamin A and D interaction was observed.

CONCLUSION

In pregnant individuals with overweight or obesity, maternal vitamin A and D concentrations declined across pregnancy, while vitamin E increased. Vitamin A insufficiency, vitamin D deficiency/insufficiency, and macrosomia were common. Maternal fat-soluble vitamin levels were not independently associated with birth weight, suggesting that vitamin status during mid- to late pregnancy may not be a major determinant of fetal growth in this metabolically high-risk population.