From the Guidelines
Yes, it is generally safe to supplement vitamin D during pregnancy, with a recommended daily intake of 600-2000 IU, and a target 25-hydroxy vitamin D concentration above 20 ng/mL (50 nmol/L) 1.
Importance of Vitamin D Supplementation
Vitamin D supplementation is crucial during pregnancy as it aids in calcium absorption, supporting the development of the baby's bones and teeth, and plays a role in immune function, potentially reducing the risk of pregnancy complications like preeclampsia and gestational diabetes.
Recommended Intake and Monitoring
The best approach is to have vitamin D levels checked through a blood test and follow the healthcare provider's specific recommendations for supplementation. Most women can safely take vitamin D supplements with food once daily.
Safety and Potential Side Effects
Side effects are rare at recommended doses, but taking excessive amounts (typically over 4000 IU daily for extended periods) could potentially cause problems. Always inform the healthcare provider about all supplements being taken during pregnancy.
Additional Considerations
For women who have undergone bariatric surgery, it is recommended to maintain a vitamin D concentration of 50 nmol/L or greater, with a serum PTH within normal limits 1.
Preconception and Pregnancy Care
Preconception care should include discussing vitamin D supplementation, and women planning to become pregnant should take additional folic acid and have their vitamin B12 levels measured before conception 1.
Key Points for Supplementation
- Daily intake: 600-2000 IU of vitamin D.
- Target concentration: Above 20 ng/mL (50 nmol/L) of 25-hydroxy vitamin D.
- Monitoring: Regular blood tests to check vitamin D levels and adjust supplementation as needed.
- Safety: Inform the healthcare provider about all supplements and avoid excessive intake.
From the Research
Safety of Vitamin D Supplementation During Pregnancy
- The safety of vitamin D supplementation during pregnancy is a topic of ongoing debate, with some studies suggesting benefits and others raising concerns about potential risks 2, 3, 4, 5, 6.
- A study published in 2011 found that circulating 25-hydroxyvitamin D levels should be 40-60 ng/ml during pregnancy, and a daily intake of 4000 IU vitamin D3 is required to attain that level 2.
- Another study published in 2020 found that vitamin D supplementation during pregnancy may improve fetal growth and reduce the risks of small-for-gestational-age, preeclampsia, preterm birth, and gestational diabetes 3.
- However, a review published in 2016 found that the evidence on whether vitamin D supplementation should be given as part of routine antenatal care to all women to improve maternal and infant outcomes remains unclear 4.
- A more recent review published in 2020 found that vitamin D supplementation policies during pregnancy and implementation of policies vary within and between jurisdictions, and regulatory authorities have cited insufficient evidence to establish pregnancy-specific targets for serum 25(OH)D concentrations or prenatal vitamin D intake 5.
- The most recent review published in 2024 found that supplementation with vitamin D during pregnancy may reduce the risk of severe postpartum haemorrhage and low birthweight, but the evidence is very uncertain and more research is needed to confirm these findings 6.
Potential Benefits and Risks
- Potential benefits of vitamin D supplementation during pregnancy include:
- Improved fetal growth
- Reduced risk of small-for-gestational-age
- Reduced risk of preeclampsia
- Reduced risk of preterm birth
- Reduced risk of gestational diabetes
- Reduced risk of severe postpartum haemorrhage
- Reduced risk of low birthweight
- Potential risks of vitamin D supplementation during pregnancy include:
- Nephritic syndrome
- Hypercalcaemia
- Hypercalciuria
- However, the evidence on these potential risks is very uncertain and more research is needed to confirm these findings.
Recommendations
- The current evidence suggests that vitamin D supplementation during pregnancy may be beneficial, but the optimal dosage and duration of supplementation are unclear 2, 3, 4, 5, 6.
- More research is needed to establish pregnancy-specific targets for serum 25(OH)D concentrations or prenatal vitamin D intake and to confirm the potential benefits and risks of vitamin D supplementation during pregnancy 5, 6.