Vitamin D during pregnancy tied to birth weight, preterm birth risk

The mean rate of change in plasma 25-hydroxyvitamin (25[OH]D) during pregnancy is predictive of birth weight z-scores and is associated with the risks for large for gestational age (LGA) and preterm birth, suggests a recent study.

The investigators evaluated the association between vitamin D serum concentrations during pregnancy and neonatal outcomes in a prospective cohort of 180 healthy Brazilian pregnant women. Participants were followed and had their 25(OH)D measured at 5–13 (baseline), 20–26, and 30–36 gestational weeks. Outcomes measured were birth weight (BW), birth length (BL), BW z-scores, BL z-scores, first minute Apgar, small for gestational age (SGA), LGA, and preterm birth.

The investigators then estimated multiple linear and Poisson regression models and determined the association between the mean rate of change in vitamin D during pregnancy concentrations and neonatal outcomes using best linear unbiased prediction of random coefficients model.

Mean BW was 3,300 g, BW z-score 0.34, BL 49.3 cm, BL z-score 0.44, and first minute Apgar score 8.2. Prevalence of SGA was 6 percent, LGA 18 percent, and preterm birth 13 percent. A direct association was observed between 25(OH)D and the risk of preterm birth at all trimesters. Incidence rate ratios (IRR) for the first, second, and third trimester were 1.02, 1.05, and 1.04, respectively.

The mean rate of change in 25(OH)D during pregnancy showed a direct association with BW z-score (β, 0.36, 95 percent confidence interval [CI], 0.07–0.65), LGA risk (IRR, 1.97, 95 percent CI, 1.07–3.63) and preterm birth (IRR, 7.35, 95 percent CI, 2.99–18.07).