Vitamin D Deficiency Increases the Risk of Stunting and Other Adverse Pregnancy Outcomes: Results from a Perinatal Cohort Study in Kenya

Abstract

Objectives: Vitamin D may protect against adverse pregnancy outcomes. The prevalence of vitamin D deficiency in pregnant women in sub-Saharan Africa has not been extensively studied and no studies have examined vitamin D status at multiple time points during pregnancy and their association with birth outcomes. Methods: We examined the prevalence of vitamin D deficiency (<50 nmol/L) and insufficiency (<75 nmol/L) in women during pregnancy, and their associations with adverse perinatal outcomes in Kenya. Serum 25-hydroxyvitamin D (25(OH)D) was measured at enrollment and at three additional time points during pregnancy, at delivery, and in cord blood. Binomial and linear regression was used to examine associations between maternal vitamin D status and adverse pregnancy outcomes. Results: A total of 21% of women had vitamin D deficiency and 51% had insufficiency at enrollment. Vitamin D status improved during pregnancy; only 11% had vitamin D deficiency and 32% had insufficiency at delivery. However, 30% and 74% of the cord blood samples had vitamin D deficiency and insufficiency, respectively. Maternal vitamin D concentrations were also associated with significantly higher weight-for-age and weight-for-length Z-scores in the newborns with mean increases of 0.1 and 0.2 per 10 nmol/L serum 25-hydroxyvitamin D, respectively. Further, maternal vitamin D deficiency was associated with a 4-fold increase in the risk of stunting among the neonates (p=0.018). Conclusions: Vitamin D insufficiency is common in pregnant women in Kenya and predicts neonatal birth size. Further research is needed on methods of improving vitamin D status during pregnancy in sub-Saharan Africa.