Calcium Supplementation in Pregnancy for Low Dietary Intake
For pregnant women with dietary calcium intake less than 800 mg per day, supplement with 1.5–2 g of elemental calcium daily, divided into multiple doses of no more than 500 mg each, taken with meals using calcium carbonate as the preferred formulation. 1, 2
Recommended Dosage
The WHO strongly recommends 1.5–2.0 g elemental calcium daily for pregnant women in populations with low dietary calcium intake (<800-900 mg/day) to prevent preeclampsia, a leading cause of maternal mortality. 1, 2, 3
If the full 1.5–2.0 g dose is impractical, a minimum of 1.0–1.5 g elemental calcium daily is advised, adjusted to local dietary patterns and adherence considerations. 1, 2
This recommendation reduces preeclampsia risk by approximately 50% in populations with low baseline calcium intake, while also lowering rates of preterm birth and improving neonatal birth weight. 2, 4
Optimal Formulation and Administration
Calcium carbonate is the preferred calcium salt because it provides 40% elemental calcium by weight (versus 21% for calcium citrate), making it more cost-effective and requiring fewer tablets. 2, 5
Divide the total daily dose into 2–3 administrations, each containing ≤500 mg elemental calcium, to maximize fractional absorption, which declines significantly with larger single doses. 2, 5
Take calcium carbonate with meals, as gastric acid is required for optimal absorption. 2, 5
Timing of Initiation
- Begin supplementation at the first antenatal contact (regardless of gestational age) and continue through delivery; early initiation may further support placental vascular development. 2, 6
Co-Administration with Iron-Folic Acid
Instruct patients to take calcium supplements together with iron-folic acid (IFA) tablets at the same time to simplify the regimen and improve adherence. 2, 5
Although calcium can acutely inhibit iron absorption in vitro, real-world studies show minimal clinical impact, and the adherence benefit of combined dosing outweighs theoretical concerns. 2, 3
Do not counsel women to take calcium and IFA separately, as this creates an unnecessary barrier and reduces compliance. 2, 3
Special Populations: Calcium Citrate
Reserve calcium citrate for women with achlorhydria, those on proton-pump inhibitors, or those unable to take supplements with meals. 2, 5
When using calcium citrate, prescribe roughly 7.1 g of the salt daily to deliver 1.5 g elemental calcium (or 9.5 g for 2.0 g elemental), divided into 3–4 doses. 2
Calcium citrate can be taken with or without food, which is its principal advantage over calcium carbonate. 2, 5
Safety Considerations and Common Pitfalls
Never administer the entire daily calcium dose as a single tablet; this leads to poor absorption and diminishes clinical benefit. 2, 5
The upper safety limit for elemental calcium is 2,000–2,500 mg per day; exceeding this may increase the risk of cardiovascular events and kidney stones. 2, 5
Common side effects include constipation and abdominal bloating; counsel patients and offer stool softeners if needed. 2, 5
Clinical Context
The total recommended calcium intake for pregnant women aged ≥19 years is 1,000–1,200 mg per day from all sources (diet plus supplements). 2, 7
Women who chronically consume suboptimal amounts of calcium (<500 mg/day) may be at risk for increased bone loss during pregnancy and require supplementation to meet both maternal and fetal bone requirements. 8