Vitamin D did not protect pregnant women against gestational hypertension or preeclampsia, according to a study published in The BMJ.
Maria C. Magnus, PhD, senior research associate in epidemiology at University of Bristol in the United Kingdom, and colleagues performed a multivariable regression analysis on data from 7,389 women from two European pregnancy cohorts. Women were excluded if they had multiple births or hypertension before pregnancy. Of these women, 751 had gestational hypertension and 135 had preeclampsia. Antenatal 25-hydroxyvitamin D, or 25-(OH)D, levels were also assessed in this review.
In a mendelian randomization analysis, researchers reviewed data from 3,388 women with preeclampsia and 6,059 controls from two case-controlled studies. Four single nucleotide polymorphisms in genes associated with vitamin D synthesis and metabolism were used as genetic instruments.
Gestational hypertension and preeclampsia were defined in both cohorts by routine BP and proteinuria measurements.
In the multivariable regression analysis, there was a weak linear association between preeclampsia and each 10% decrease in 25-(OH)D level (pooled adjusted RR = 1.03; 95% CI, 1-1.07). Compared with women with a 25-(OH)D level greater than 75 nmol/L, those with a level less than 25 nmol/L had an increased risk for preeclampsia (pooled aRR = 2.04; 95% CI, 1.02-4.07).
Strong evidence was not found related to the link between 25-(OH)D and gestational hypertension.
In the mendelian randomization analysis, researchers did not find strong evidence on the linear effect of a 10% decrease in 25-(OH)D on gestational hypertension (OR = 0.9; 95% CI, 0.78-1.03) or preeclampsia (OR = 1.19; 95% CI, 0.92-1.52).
A formal two-sample mendelian randomization analysis found no evidence of a causal linear effect between preeclampsia and a 10% decrease in 25-(OH)D level (OR = 0.98; 95% CI, 0.89-1.07). Women with a 25-(OH)D level less than 75 nmol/L had an OR for preeclampsia of 0.96 (95% CI, 0.8-1.15), whereas those with levels less than 50 nmol/L had an OR of 0.93 (95% CI, 0.73-1.19).
“Mendelian randomization studies with a greater number of women with preeclampsia will provide additional evidence to support or negate a causal effect of vitamin D in preeclampsia,” Magnus and colleagues wrote. “The next step (should such an effect be likely) would require large, well-conducted trials of vitamin D supplementation. In particular, it is important to find out whether the benefit of vitamin D supplementation varies by ethnic group — most studies to date have included only individuals of European origin — and a broad range of baseline 25-hydroxyvitamin D levels.” – by Darlene Dobkowski
Disclosures: Magnus reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.