Iron supplementation for non-anaemic pregnant women and the incidence of hypertensive disorders in pregnancy: A systematic review and meta-analysis

Objective: To investigate effect of iron supplementation on the risk of hypertensive disorders in pregnancy in non-anaemic pregnant women. Methods: A literature search was conducted using three categories of terms with its synonyms or related words: "iron", "supplement", "hypertensive disorders in pregnancy" through MEDLINE (OVID), CINAHL, PubMed, Cochrane Library, Scopus, Web of Science, ICTRP, and ClinicalTrials.gov, and manual search of references was used in seven potential resources. The inclusion criteria were randomized control trials (RCTs), published in English, full-text available, having healthy pregnant women without anaemia for study participants, and having hypertensive disorders in pregnancy at the end of pregnancy as the outcome. The risk of bias assessment tool was used for quality appraisal. Meta-analysis was conducted by calculating the fixed and random effects of the odds ratio (OR) for iron supplementation among non-anaemic pregnant women compared with the incidence of hypertensive disorders in pregnancy. The range of the study's estimation accuracy was reflected by a 95% confidence interval (CI). Results: Four RCTs were included in the meta-analysis. The pooled results showed that iron supplementation possibly had no effect on the incidence of hypertensive disorders in pregnancy (OR 0.93, 95% CI 0.81-1.07; P=0.30), gestational hypertension (OR 1.37, 95% CI 0.69-2.73; P=0.36) as well as on the development of preeclampsia (OR 1.45, 95% CI 0.71-2.97; P=0.31). Conclusions: Iron supplementation has no effect on the incidence of hypertension in non-anaemic pregnant women. In general, there is a lack of evidence for the association between iron supplementation and the incidence of hypertensive disorders in pregnancy among non-anaemic pregnant women, and further studies are needed.