P4 - The relationship between vitamin D supplementation before 24 weeks gestation and risk of preeclampsia

Abstract

A growing body of evidence suggests that there may be a relationship between vitamin D (VD) levels and the development of pre-eclampsia. Despite the growing body of primary studies, systematic reviews on the topic have yielded contradictory results. The aim of this systematic review was to analyse the existing literature to determine whether or not vitamin D supplementation prior to 24 weeks gestation has an impact on preeclampsia risk when compared to a non-intervention or placebo control group. The review was conducted using the methodology outlined in the Joanna Briggs Institute manual for evidence synthesis. The use of a structured and validated methodology aided in ensuring rigorous analysis and synthesis of the existing literature to develop recommendations which can inform practice. Medline and CHINAL databases were searched for suitable studies using a predetermined search string, with only randomised control trials being included for review. Journals were searched from their conception to the first of July 2021. Quality of included studies was assessed using the critical appraisal skills (CASP) checklist for randomised control trials. Five randomised control trials were included in the review and meta-analysis. Vitamin D supplementation prior to 24 weeks gestational age was associated with a significantly reduced risk of preeclampsia (OR:0.51, [95%CI: 0.4-0.67]). Vitamin D supplementation was not associated with adverse outcomes or vitamin D toxicity even at doses equivalent to >7000IU per day. The results of this review suggest that vitamin D supplementation beginning prior to 24 weeks gestation is effective in reducing the risk of preeclampsia. This presents the opportunity for a safe, accessible and cost-effective measure for reducing rates of preeclampsia and promoting normal physiological pregnancy. As champions of normal physiological midwives play a key role in the implementation of this research into practice.