The Association of Maternal Asthma and Early Pregnancy Vitamin D with Risk of Preeclampsia: An Observation From Vitamin D Antenatal Asthma Reduction Trial (VDAART).

Background: Maternal asthma, uncontrolled asthma, and low vitamin D levels during pregnancy have been individually linked to increased risk of preeclampsia.

Objective: To investigate the association of history of physician-diagnosed asthma and uncontrolled asthma status during pregnancy with the risk of preeclampsia and the effects of early pregnancy vitamin D concentrations on this relationship.

Methods: A total of 816 subjects with available pregnancy outcome data and risk factors of interest were analyzed. A group of experienced obstetricians and gynecologists from 3 study centers validated the preeclampsia diagnoses. Vitamin D was measured using the DiaSorin method at 10 to 18 weeks of gestation. The Pregnancy-Asthma Control Test was used to assess asthma control during pregnancy. Criterion-based stepwise variable selection algorithm was applied to investigate the relationships of risk factors of interest (history of asthma diagnosis, uncontrolled asthma during pregnancy, and vitamin D) to preeclampsia.

Results: The incidence of preeclampsia was not related to the presence of asthma diagnosis (8.9% with vs 7.4% without). The adjusted odds of preeclampsia controlled for maternal serum 25-hydroxyvitamin D (25OHD) concentrations was higher for women with a higher proportion of uncontrolled asthma months per visit during pregnancy (adjusted odds ratio, 3.55; 95% CI, 1.15-13.0). Adjusting for asthma control status during pregnancy, an additional decrease in the associated preeclampsia risk by 7% was observed for a 10-unit (ng/mL) increase in early pregnancy 25OHD levels (adjusted odds ratio, 0.60; 95% CI, 0.43-0.82) as compared with the previous risk estimate of preeclampsia associated with low maternal 25OHD unadjusted for asthma control status.

Conclusions: Uncontrolled asthma during pregnancy is associated with an increased risk of preeclampsia. Early pregnancy 25OHD contributes to the association of uncontrolled asthma status with preeclampsia.