What is the role of calcium in pregnancy?

Calcium's Role in Pregnancy

Calcium supplementation during pregnancy is crucial for preventing preeclampsia, with recommended doses of 1.0-1.5g elemental calcium daily for women with low calcium intake. 1, 2

Importance of Calcium in Pregnancy

Calcium serves several critical functions during pregnancy:

• Prevention of preeclampsia: Calcium supplementation reduces the risk of preeclampsia by approximately 50%, particularly in women with low dietary calcium intake 1
• Fetal skeletal development: Approximately 30g of calcium is transferred to the fetus during gestation for bone formation 1
• Maternal bone health maintenance: Helps prevent depletion of maternal calcium stores during pregnancy 3

Recommended Calcium Intake

• WHO recommendation: 1.5-2.0g elemental calcium daily from 20 weeks gestation 1, 2
• Practical recommendation: 1.0-1.5g elemental calcium daily is likely sufficient and may improve adherence 1
• Administration: Calcium should be taken in divided doses of ≤500mg per administration for optimal absorption 1
• Formulation: Calcium carbonate is the most cost-effective choice in most settings 1, 2

Timing of Supplementation

• Traditional recommendation: Start at 20 weeks gestation (based on clinical trials) 1
• Practical approach: Begin at first antenatal contact, regardless of gestational age 1
• Duration: Continue until delivery 1, 2

Calcium and Iron Supplementation

• While calcium can inhibit iron absorption in short-term studies, the clinical effect over longer periods is minimal 1
• To simplify regimen and improve adherence, calcium and iron-folic acid supplements can be taken together rather than requiring separate administration times 1

Risk Assessment and Targeting

• Most low and middle-income countries have mean calcium intake <900mg/day 1
• Supplementation is particularly important for women at higher risk of preeclampsia:
  • Prior preeclampsia
  • Chronic hypertension
  • Pregestational diabetes
  • BMI >30 kg/m²
  • Multiple pregnancies
  • Nulliparity 2

Potential Side Effects

• Rare association with HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) 1
• Possible postnatal bone resorption that persists through lactation 1, 4
• High doses may potentially increase cardiovascular disease risk compared to lower doses 1

Special Considerations

• Calcium intake interacts with vitamin D status to affect fetal bone development 5
• Optimal calcium intake and adequate vitamin D status are both needed to maximize fetal bone growth 5
• Pregnancy and lactation are associated with major changes in calcium metabolism and bone mineral status 6

Implementation Approach

1. Assess dietary calcium intake when possible (assume inadequate in most low-income settings)
2. Prescribe calcium carbonate at 1.0-1.5g daily in divided doses
3. Begin at first antenatal contact and continue until delivery
4. Combine with dietary counseling on calcium-rich foods when available
5. Monitor for preeclampsia and other pregnancy complications

The benefits of calcium supplementation during pregnancy significantly outweigh the potential risks, particularly in populations with low dietary calcium intake 1, 7.