Should women take supplements while pregnant?

It seems there's an endless amount of online information related to what supplements a woman should take when pregnant. As a result, searching for reliable information related to supplements during pregnancy can be difficult at best.

Here's a Q&A with some advice on which supplements you can use — and those you should avoid — during your pregnancy:

Are dietary supplements OK during pregnancy?

It's recommended that women should not use dietary and herbal supplements during pregnancy. In addition, dietary and herbal supplements should be used with caution in women of reproductive age due to the risk of taking these supplements before knowledge of pregnancy.

Unlike prescription drugs, dietary supplements are not reviewed by the U.S. Food and Drug Administration (FDA) for safety and effectiveness. As a result, they may contain contaminants, like metals, pesticides, chemicals or bacteria, which may pose risks for pregnancy. Also, most supplements are not thoroughly studied, which can lead to issues related to quality standards for ingredients and strength. For example, vinpocetine — an ingredient found in a number of dietary supplements, including those marketed for weight loss, enhanced memory, focus, mental acuity or increased energy — is not safe during pregnancy. Other commonly used supplements that may cause harm during pregnancy include melatonin and St. John's wort.

What about meal replacement shakes?

Women shouldn't consume nutritional shakes as meal replacement options during pregnancy, as they're considered supplements and are not approved by the FDA.

Nutritional shakes may contain vitamins, herbs or other substances that have the potential to be harmful during pregnancy, and are difficult to identify on a label. Many supplement labels often read as herbal or proprietary blends. Also, because these shakes are considered supplements, there are similar quality, contamination, safety and efficacy concerns as with other dietary supplements.

What supplements are OK to take?

Folic acid supplementation is recommended for all women of reproductive age and who are pregnant, as it helps prevent neural tube defects or abnormalities, such as spina bifida. Ideally, women should take a daily folic acid supplement for at least one month before conception.

Ginger has also been shown to be helpful for nausea and vomiting during pregnancy. The American College of Obstetricians and Gynecologists suggests using ginger capsules to treat nausea and vomiting during pregnancy.

What about vitamins during pregnancy?

A prenatal vitamin should be a sufficient source of vitamins during a woman's pregnancy. Talk to your health care provider about a prescription for a prenatal vitamin that is approved for use prior to getting pregnant and during pregnancy. Once pregnant, women should avoid taking more than twice the recommended dietary allowances of vitamins and minerals. Excessive intake of vitamins and minerals, such as iodine, can cause problems in pregnancy.

Also, an excessive intake of vitamin A, defined as more than 10,000 IU of vitamin A per day, may be associated with fetal malformations of the bones, urinary tract or nervous system. As a result, women should not take additional vitamin A supplementation outside of what's in their prenatal vitamin.

In general, how can women be healthy during pregnancy?

Women who are pregnant should strive to eat a well-balanced diet that is high in vegetables and fruits, has lots of colors, and includes whole grains and lean meats. Finally, make sure to avoid highly processed foods and foods high in fats, such as fried and sugary foods.

It's essential for women who are pregnant or who have the potential to become pregnant to let their health care provider know if they are taking any supplements, and discuss the risks and benefits of continuing them.

By Mayo Clinic Health System staff.