Vitamin D Supplementation and Sun Exposure Maintain Blood Pressures of Pregnant Women and Increase Birth Weight in a Randomized Controlled Trial

BACKGROUND: Vitamin D supplementation or sun exposure increase pregnant women’s Calcidiol levels, lower the blood pressures and increase birth weight. We aimed to compare the effects between sun exposure and vitamin D supplementation on pregnant women’s Calcidiol levels, blood pressures and newborns’ anthropometric indices. METHODS: This randomized clinical trial was conducted on 108 pregnant women at 20 wk of gestation on 2021’s dry season in Semarang City, Indonesia. The subjects were randomly and evenly divided into 3 groups of 36 subjects (sunlight exposure, vitamin D supplement, and control). Vitamin D group received 1000 IU daily and sun exposure group was recommended to have 15–30 min for 3 times/week for 17 wk. Compliance was monitored every 2 d through home visits. Calcidiol levels, blood pressures, in all groups were compared before and after intervention. The increments and the newborn anthropometric indices were compared between the groups and controlled for confounding factors. RESULTS: At baseline, all groups had vitamin D deficiency, different mean Calcidiol levels, systolic, and diastolic blood pressures. The mean Calcidiol levels increased in the sun exposure and vitamin D group after the intervention. Systolic blood pressure decreased in the vitamin D group only (P=0.019). The mean birth weight was the highest in the vitamin D group (3,172±181.8 g) compared to the sun exposure (3,091±362.5g) and control groups (2,861 ± 208.0 g). CONCLUSION: Vitamin D supplementation and sun exposure increased Calcidiol levels and birth weights. Vitamin D supplementation maintained systolic blood pressure.