Calcium Supplementation in Pregnancy: A Systematic Review of Clinical Studies

Background and Objectives: Calcium is an essential mineral that plays a vital role in fetal development and maternal health during pregnancy. The World Health Organization recommends a daily calcium intake of 1.5-2 g for pregnant adult women. Calcium deficiency during gestation may lead to complications, such as gestational hypertension, preeclampsia, loss of bone mineral density, impaired fetal development, and other adverse pregnancy outcomes. The aim of the present review is to evaluate the current clinical evidence on calcium intake during pregnancy. Methods: The present systematic review was conducted according to the PRISMA 2020 statement by searching two major databases, PubMed and Mendeley. The study protocol was registered in the Open Science Framework (DOI: osf.io/rvj7z). Inclusion criteria were clinical trials on calcium supplementation during pregnancy. Exclusion criteria were clinical guidelines, reviews, case reports, case series, letters, and commentaries. The Newcastle-Ottawa Scale was used to assess the risk of bias in the included studies. Results: Initially, 451 publications were identified, and after removal of duplicates and screening of titles and/or abstracts and/or full texts, 34 studies were included. The number of participants ranged between 30 and 22,000 women. Calcium supplementation was associated with lower incidence of and less severe gestational hypertension and preeclampsia, lower risk of preterm birth, longer pregnancy duration and higher neonatal birth weight, and improved maternal bone mineral density postpartum. When the doses were split up into smaller doses, the benefits were strongest with high-dose regimens (1.5-2 g/day). Conclusions: Calcium supplementation during pregnancy has beneficial effects on maternal and neonatal health, especially in populations with insufficient dietary daily calcium intake and women at high risk of hypertensive disorders. Daily dose may vary according to individual needs, daily dietary calcium intake, and general health status. Further large-scale randomized controlled trials (RCTs) are necessary to confirm these findings.