Is first trimester vitamin D status in nulliparous women associated with pregnancy related hypertensive disorders?

Objectives: this study aimed to explore if maternal vitamin D status in early pregnancy was associated with pre-eclampsia and pregnancy-induced hypertension. Relationships between vitamin D status and blood pressure at the start of pregnancy as well as the occurrence of a mid-pregnancy drop in blood pressure were also explored. This secondary analysis was completed to investigate a possible mechanism for the association between vitamin D status and pregnancy related hypertensive disorders.

Design And Setting: data were obtained from the Amsterdam Born Children and their Development study, a prospective community-based cohort study based in Amsterdam, The Netherlands.

Participants: a total of 2074 nulliparous women without pre-existing hypertension and with a known vitamin D status before 17 weeks gestation were included in the study. Vitamin D status was categorized into four groups: "normal" (≥50nmol/L), "insufficient" (30-49.9nmol/L) "deficient" (20-29.9nmol/L) or "severely deficient" (<20nmol/L).

Measurements: logistic regression analysis was used to investigate if vitamin D status was related to the odds of experiencing pre-eclampsia or pregnancy-induced hypertension. Models were corrected for maternal age, ethnicity, pre-pregnancy BMI, smoking and socioeconomic status. χ(2) and ANOVA tests were used to investigate relationships between vitamin D status and the blood pressure parameters.

Findings: when compared to women with a normal vitamin D status, women who were severely deficient had an increased risk for pre-eclampsia (OR 2.08; 95% CI, 1.05-4.13), but the association was rendered non-significant after correction (OR 1.88; 95% CI 0.79-4.48). There were no associations between vitamin D status and pregnancy-induced hypertension, starting blood pressure or the occurrence of a mid-pregnancy drop in blood pressure.

Key Conclusions: no strong evidence was found for an association between first trimester vitamin D status and pregnancy related hypertensive disorders in nulliparous women.

Implications For Practice: at this time, vitamin D supplementation is not warranted for the specific purpose of preventing pregnancy related hypertensive disorders.