Vitamin D deficiency linked to preterm births
Vitamin D insufficiency is associated with the risk of preterm births, a new meta-analysis reports. However, there is little evidence to link stillbirths and spontaneous abortions to vitamin D levels.
PubMed and Scopus were searched for original, longitudinal epidemiologic studies regarding vitamin D status and adverse pregnancy outcomes. Only those conducted in humans and those that assessed vitamin D levels through laboratory methods were included.
Studies involving nonsingleton pregnancies and mothers with conditions like HIV and pre-eclampsia were excluded. The Newcastle-Ottawa Scale was used to evaluate the methodological quality of the studies selected.
A total of 18 studies were included. Of these, eight were of very high quality, three had high quality, four had satisfactory quality and three had low quality. Because vitamin D levels were measured through laboratory techniques, the risk of information bias was low.
There was an 83-percent (95 percent CI, 1.23 to 2.74) increased risk of preterm births at <32 to 34 weeks and a 13-percent increased risk (0.94 to 1.36) at <35 to 37 weeks associated with serum 25(OH)D levels <75 nmol/l.
Decreasing levels of serum 25(OH)D was associated with significant increases in the risk of preterm births (50 to 75 nmol/l: summary relative risk [RR].1.25; 1.04 to 1.49; <50 nmol/l: summary RR, 1.36; 1.04 to 1.78).Furthermore, an 11-percent increased risk of spontaneous preterm births at <35 to 37 weeks was associated with serum 25(OH)D levels of<75 nmol/l (RR, 1.11; 0.75 to 1.65).
The risk of stillbirths (RR, 1.02; 0.96 to 1.09), spontaneous abortions (RR, 1.04; 0.95 to 1.13), short gestational lengths (effect size [ES], -0.24; -0.69 to 0.22) and low Apgar scores were not associated with vitamin D insufficiency.