Influence of vitamin D serum concentration, prenatal care and social determinants on birth weight: a northeastern Brazilian cohort study

The relationship among social determinants, vitamin D serum concentration and the health and nutrition conditions is an important issue in the healthcare of pregnant women and newborns. Thus, the present study analyses how vitamin D, prenatal monitoring and social determinants are associated with birth weight. The cohort comprised 329 pregnant women, up to 34 weeks gestational age at the time of admission, who were receiving care through the prenatal services of Family Health Units. Structural equation modelling was used in the statistical analysis. The mean birth weight was 3340 (sd 0 center dot 545) g. Each nmol increase in maternal vitamin D serum concentration was associated with an increase in birth weight of 3 center dot 06 g. Prenatal healthcare with fewer appointments (beta -41 center dot 49 g, 95 % CI -79 center dot 27, -3 center dot 71) and late onset of care in the second trimester or third trimester (beta -39 center dot 24 g, 95 % CI -73 center dot 31, -5 center dot 16) favoured decreased birth weight. In addition, low socio-economic class and the practice of Afro-Brazilian religions showed a direct association with high vitamin D serum concentrations and an indirect association with high birth weight, respectively. High gestational BMI (beta 23 center dot 84, 95 % CI 4 center dot 37, 43 center dot 31), maternal education level (beta 24 center dot 52 g, 95 % CI 1 center dot 82, 47 center dot 23) and length of gestation (beta 79 center dot 71, 95 % CI 52 center dot 81; 106 center dot 6) resulted in high birth weight. In conclusion, maternal vitamin D serum concentration, social determinants and prenatal care, evaluated in the context of primary healthcare, directly determined birth weight.