Calcium Supplementation in Pregnancy

Introduction to Calcium Supplementation

The World Health Organization recommends initiating calcium supplementation at 20 weeks' gestation, based on the timing used in the meta-analyses that established the evidence base for preeclampsia prevention 1
Calcium supplementation should be initiated at the first antenatal care visit, regardless of gestational age, and continued until delivery 1, 2, 3

From a pragmatic standpoint, calcium supplementation should begin at the first antenatal care visit, even if this occurs before 20 weeks' gestation, to simplify the regimen and reduce complexity 2, 3
Starting calcium supplementation at the first antenatal care visit accommodates late presenters and may provide additional benefit by modulating placental vascularization and systemic vasomotor activity 2, 3
The American College of Nutrition and other health organizations support the initiation of calcium supplementation as early as possible in pregnancy to maximize its benefits 2, 3

The recommended dose is 1.0-1.5 g elemental calcium daily, divided into doses of ≤500 mg per administration to maximize absorption, as suggested by the World Health Organization and other health guidelines 4
Calcium carbonate is preferred due to cost-effectiveness and higher elemental calcium content, according to the World Health Organization 4
Calcium supplementation should be continued from first contact until delivery, as recommended by the American College of Nutrition and other health organizations 2, 4

Calcium supplementation reduces the risk of preeclampsia by approximately 50%, particularly in populations with low dietary calcium intake, as reported by the World Health Organization 4
This intervention addresses a leading cause of maternal mortality globally, highlighting the importance of calcium supplementation in pregnancy, as emphasized by the American College of Obstetricians and Gynecologists 4

The World Health Organization and other health organizations recommend not delaying supplementation waiting for 20 weeks if the woman presents earlier—start immediately 2, 3
Calcium should not be withheld from women who present after 20 weeks—supplementation beyond this timepoint is still beneficial, as suggested by the American College of Nutrition and other health guidelines 2, 3
Overly complex schedules should not be created by separating calcium from iron supplements, as this reduces adherence without clear clinical benefit, according to the World Health Organization and other health organizations 2, 3