Findings from a Randomized Controlled Trial on Vitamin D Screening and Prenatal Outcomes

Published on March 6, 2025

A study involving 1800 pregnant women found a 55% decreased risk of adverse events among women who received vitamin D based on vitamin D status

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A study by Rostami et al. was designed to determine the safety and effectiveness of different vitamin D protocols given based on baseline vitamin D status during pregnancy. A group of 900 pregnant women were followed without intervention and used as the control group, while 900 other pregnant women were included in the screening and supplementation arm. Women with vitamin D deficiency were randomized to receive different treatments based on vitamin D level, and these vitamin D supplementation ‘regimens’ were compared for safety.

In this study, moderate vitamin D deficiency was defined as a 25(OH)D level of 10 to 20 ng/ml, while severe deficiency as defined as a level below 10 ng/ml.

What did the study find?

The vitamin D level at delivery and the rate of prenatal complications was evaluated for all women.

Among the women in the non-screening group

• 98% of the pregnant women remained deficient or insufficient after standard prenatal supplementation; only 2% achieved a vitamin D level above 20 ng/ml
• Vitamin D levels at delivery were significantly lower than in the screening and treatment group, at 11 ng/ml
• None of the women achieved vitamin D levels above 30 ng/ml

Among the women in the screening group

• 53% achieved a vitamin D level above 20 ng/ml after supplementation
• Rates of preeclampsia, gestational diabetes, and preterm delivery were 60%, 50%, and 40% lower than the non-screening group
• Vitamin D levels at delivery were significantly higher, at 21 ng/ml
• Only 2.7% achieved vitamin D levels above 30 ng/ml

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Regarding preeclampsia specifically, rates increased as vitamin D levels decreased; among screening site participants the rate of preeclampsia was 1.3%, 16%, and 38.5% for women whose vitamin D levels were above 20 ng/ml, 10-20 ng/ml, and below 10 ng/ml respectively.

No preeclampsia or gestational diabetes was observed among women who achieved vitamin D levels above 30 ng/ml.

There was a significant difference in preterm birth outcomes among women who were severely deficient (decreased by 67%) and moderately deficient (decreased by 30%) at delivery.

“…screening in these women decreased the odds of adverse events by 55%.”

Behind the Research: Exclusive Interview with Dr. Bruce Hollis

Next we will share an interview with Dr. Bruce Hollis, co-author on the Rostami et al. paper, about specific study details and additional important notes regarding vitamin D during pregnancy.  Stay tuned!

Are you interested in implementing a vitamin D screening and supplementation protocol in your practice? Let us know – we can help! Reach out today.

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