747 - What is the expected improvement in maternal vitamin D status that occurs with supplementation during pregnancy? A systematic review and meta-analysis

Publication Number: 747.7024

Marisa van Arragon, University of Auckland, Auckland, Auckland, New Zealand; Robert K. Scragg, School of Population Health, University of Auckland, Auckland, Auckland, New Zealand; Cameron C. Grant, University of Auckland, Auckland, Auckland, New Zealand; Vanessa Jordan, University Of Auckland, Auckland, Auckland, New Zealand

Background: Vitamin D deficiency during pregnancy is associated with adverse pregnancy and infant health outcomes. Vitamin D supplementation is recommended during pregnancy. What is the expected increase in serum maternal 25-hydroxyvitamin D [25(OH)D] concentration that occurs with vitamin D supplementation during pregnancy?

Objective: To conduct a Cochrane Systematic Review to quantify the change in serum 25(OH)D concentration that occurs in women supplemented with vitamin D during pregnancy.

Design/Methods: The protocol for this review has been published (DOI: 10.1002/14651858.CD015111). We searched CENTRAL, PubMed, Embase, CINAHL, EBSCO, Web of Science, Global Index Medicus, Register of Controlled Trials platforms and sources of unpublished data from inception to July 2023. Included randomized controlled trials compared vitamin D versus placebo or higher dose (≥1000 IU) versus lower dose (≤1000 IU) vitamin D supplementation, given from early pregnancy up to age 5 years. For this objective we included studies where the intervention was given to pregnant women and the outcome was measured from maternal serum at end of treatment, either during the third trimester of pregnancy, at delivery, or up to 6 weeks postpartum.

Results: From 5434 records screened, we included 107 studies (n=31,521) in the review, with 42 (n= 7943) studies reporting on serum 25(OH)D levels in women when the intervention was given anytime during pregnancy. Seventeen studies compared vitamin D versus placebo, and twenty-five compared higher versus lower dose vitamin D. Included randomized controlled trials were published between 1980-2023, reporting data from all World Health Organization global regions. Dosages ranged from 400 to 5000 IU/daily (or daily equivalent when given weekly, two weekly or monthly) and treatment duration varied from six to 35 weeks.
In the vitamin D versus placebo studies, the mean difference (MD) in maternal 25(OH)D concentration was 28.73 nmol/L [95% confidence interval (CI) 27.33 - 30.12 nmol/L], 17 studies, n=2680, I²=99%, favoring the vitamin D group. In ng/mL, the MD (95% CI) was 11.49 ng/mL (10.93 - 12.04 ng/mL).
In the higher versus lower dose studies, the MD in maternal 25(OH)D concentration was 26.90 nmol/L (95% CI 25.22 - 28.57), 25 studies, n=5263, I²=92%, favoring the higher dose group. In ng/mL, the MD (95% CI) was 10.76 ng/mL (10.09 - 11.43 ng/mL).

Conclusion(s): Vitamin D supplementation during pregnancy increases maternal serum 25(OH)D concentration by at least 27 nmol/L (10.8 ng/mL) in comparison to placebo and by at least 25 nmol/L (10 ng/ml) when a higher dose is compared to a lower dose of vitamin D.