The effect of pregnancy vitamin D supplementation on maternal blood pressure: real-world data analysis within the MAVIDOS randomised placebo-controlled trial

Observational studies have suggested negative associations between maternal 25-hydroxyvitamin D (25(OH)D) status and risk of hypertensive disorders of pregnancy [pregnancy-induced hypertension (PIH) and preeclampsia (PET)]. Data from intervention studies are limited. We hypothesised that vitamin D supplementation would lower maternal blood pressure (BP) during pregnancy and reduce the incidence of hypertensive disorders of pregnancy.

The Maternal Vitamin D Osteoporosis Study (MAVIDOS) was a randomised placebo-controlled trial. Pregnant women with a baseline 25(OH)D of 25–100 nmol/l were randomized to either 1000 IU/day cholecalciferol or placebo from 14 to 17 weeks’ gestation until delivery. BP recordings documented during routine clinical pregnancy care were obtained from clinical records and grouped into gestational windows based on the schedule for routine antenatal care in the United Kingdom (23⁺⁰–24⁺⁶, 27⁺⁰–28⁺⁶, 33⁺⁰–35⁺⁶, 37⁺⁰–38⁺⁶, 39⁺⁰–40⁺⁶ and ≥ 41⁺⁰ weeks^+days). Systolic and diastolic BP measurements in these gestational windows were compared between randomisation groups. Diagnoses of PIH or PET (in accordance with national guidelines) and the use of antihypertensive agents were also noted and compared between groups.

Data for 734 women (366 cholecalciferol, 368 placebo) were included. Maternal mean systolic and diastolic BP did not differ between the randomization groups at any of the gestations studied. The incidences of PIH (placebo 1.6%, cholecalciferol 3.6%, p = 0.10) and PET (placebo 3.3%, cholecalciferol 3.8%, p = 0.68) were similar between the two groups.

Gestational vitamin D supplementation with 1000 IU/day from 14 to 17 weeks gestation did not lower maternal BP or reduce the incidences of PIH or PET in this trial.