The impact of maternal 25(OH)D on fetal growth and adiposity: the Araraquara Cohort Study

Abstract The biologically active form of vitamin D (1,25(OH) 2 D) is involved in the regulation of calcium and phosphorus, influencing bone formation and probably fetal growth and development. However, 1,25(OH) 2 D has a very short half-life, and 25(OH)D is the main circulating metabolite, making it the ideal clinical indicator. Given the lack of prospective epidemiological cohort studies exploring the relationship between maternal 25(OH)D and fetal growth and adiposity, the aim of this study was to evaluate the association of maternal 25(OH)D concentrations with fetal biometry and adiposity at three periods of pregnancy. This prospective study included 330 women participating in the Araraquara Cohort Study, Brazil, who were evaluated at gestational ages ≤19, 20–28 and ≥30 weeks. 25(OH)D concentrations were measured by chemiluminescence. The following fetal outcomes were assessed by ultrasound: biometric (estimated fetal weight, femur length, abdominal circumference, head circumference and biparietal diameter) and adiposity parameters (subcutaneous tissue of the abdomen and subcutaneous areas of the thigh and arm). Generalised estimating equation models adjusted for maternal sociodemographic, lifestyle, nutritional, clinical and biochemical factors were used. In the unadjusted analysis, 25(OH)D ≥ 75 nmol/l was associated with higher fetal biometry and adiposity measures. After adjusting for potential confounders, for each increase of 10 nmol/l in 25(OH)D, there was a 0·0046 cm increase in fetal head circumference ( β = 0·0046 [95 % CI 0·0003, 0·0089]; p = 0·04). Maternal 25(OH)D was associated with greater head circumference, suggesting a possible role of 25(OH)D in fetal cranial development and reinforcing the importance of implementing prenatal monitoring of 25(OH)D concentrations.