Vitamin D is an essential vitamin during pregnancy. You need vitamin D to absorb calcium, which your baby needs for strong bones. Low levels of vitamin D during pregnancy have been linked to high blood pressure (preeclampsia), low birth weight, diabetes of pregnancy (gestational diabetes), and an increased risk of cesarean section.
The largest source of vitamin D in your body comes from sunshine. Just one-half hour of solar radiation on your skin produces about 50,000 units of vitamin D. That is why a recent study presented at the 2015 European Congress of Endocrinology is worth noting. The study looked at vitamin D levels in 2,649 pregnant Mediterranean women.
These were women living in Greece, Italy, and Spain. They should have been exposed to plenty of sunshine. But the study found that 90 percent of the women were vitamin D deficient. So what does that mean for you if you are pregnant in the winter or you live in northern parts of the United States or Canada? Vitamin D deficiency is three times more common in the winter.
Your prenatal vitamin probably has 400 international units (IU) per day of vitamin D. That may not be enough for you. The Food and Nutrition Board at the Institute of Medicine of the National Academies has set 600 IUs per day as the requirement during pregnancy and breastfeeding. The Royal College of Obstetricians & Gynaecologists advises at least 1,000 IUs per day if you are at risk for vitamin D deficiency.
What to Do?
Although they do not recommend routine blood testing for vitamin D levels, the American Congress of Obstetricians and Gynecologists do say that you should consider being tested if you are at risk for low D. You may be at risk if:
- You are a vegetarian or you are lactose intolerant. The best food sources of vitamin D are fortified milk, egg yolk, and oily fish like salmon or mackerel.
- You are pregnant in a cold, northern climate.
- You have dark skin. Melanin, the pigment in skin, absorbs about 90 percent of sunlight so it cannot be used to make vitamin D.
- You have very light skin and always use sunscreen. Sunscreen blocks vitamin D production.
- You are overweight. Obesity lowers blood levels of vitamin D.
If you are concerned about your vitamin D level, or if you are in a high risk group for vitamin D deficiency, ask you healthcare provider if you should get your level checked. Studies show that up to 60 percent of Americans may be vitamin D deficient. Vitamin D in very high doses can be toxic but levels up to 4,000 IUs have been shown to be safe during pregnancy and breastfeeding.
If your levels are low, talk to your health care provider about taking a supplement. Vitamin D comes as D2 or D3. Most experts agree that D3 is better. If your supplement does not give the D number, look for the name. D3 is cholecalciferol. D3 is the form that your body makes naturally from sunlight. It is also more potent and more stable in supplement form than D2.