If you’ve been taking natural supplements for awhile, is it safe for you to keep taking them while you’re pregnant?

The common answer is yes—but only if those supplements contain vitamins and minerals and not herbs. Many women take prenatal vitamins under the advice of their doctors to get extra folic acid into their systems. Folic acid (also known as folate) has been shown to decrease the risk of birth defects, in particular spina bifida.

Pregnant women need more nutrients than non-pregnant women. Their bodies are sustaining the healthy development of a new life, and they will need to consume more protein, calories and other nutrients than normal. But remember, although you may be eating for two, you’re not eating for two fully-grown adults! Dieticians advise that a woman only needs to eat an additional 200 calories a day (roughly the amount of calories in a low-fat cup of yogurt, for example) to keep her baby healthy.

Other nutritional supplements that a pregnant woman may need to consider are:

Iron. Pregnant women can become anemic if they aren’t getting enough iron through their diets, so an iron supplement may be advised.

Vitamin D. This essential nutrient helps the body absorb calcium more efficiently, which is important for growing bones.

Protein. Packed with iron, zinc, and vitamin B6, protein is an essential building block in muscle development and aids in the production of antibodies and hormones.

So, what about herbal supplements? No research has been done on pregnant women who have taken herbal supplements to determine if they can cause any harmful effects, but most medical experts agree that it is best to err on the side of caution. The March of Dimes, the non-profit organization dedicated to raising awareness of birth defects, has formally advised women to avoid taking herbal supplements during pregnancy. It is generally recommended that women who are pregnant make a concerted effort to get their nutrients from their diets and avoid taking herbal supplements.