Iodine is an important nutrient for pregnant women and their babies, but as many as a third of pregnant women don’t get enough in their diets, according to the American Academy of Pediatrics. This can lead to poor brain development in babies.

If you’re like many women, you don’t know much about iodine, let alone whether you’re getting adequate amounts. Learning six simple facts about this mineral will help you and your baby.

Related: 7 Foods You Shouldn’t Eat When Pregnant and 6 You Should

#1: Iodine is crucial to good health

Getting enough iodine helps your body produce thyroid hormone. (The thyroid is a gland in the neck that regulates metabolism and other important body functions.) Without the right amount of thyroid hormone in your body, your baby’s brain and nervous system may not develop properly.

Iodine helps babies in another way, too: It contributes to the proper development of their bones and central nervous systems before and after birth.

And there’s one more big benefit to iodine: Getting enough helps protect mothers and babies from the effects of certain kinds of pollution in the environment, such as pollutants found in cigarette smoke and in a small percentage of the drinking water supplies in the United States, according to the AAP.

#2: Iodine requirements go up during pregnancy and breastfeeding

We need iodine throughout our lives. But because of the important role iodine plays in the health of unborn babies, the requirements for iodine are highest during a woman’s childbearing years.

The recommended dietary allowance for iodine is 150 micrograms for an adult woman; it goes up to 220 micrograms during pregnancy and 290 micrograms during breastfeeding, according to the National Institutes of Health. 

#3: You can’t count on food for iodine

Iodine is a trace element found in ocean water and in some (but not all) soil. When crops grow in iodine-rich soil, they absorb some of it, and when we eat those foods, our bodies take it from them during digestion. However, when crops grow in iodine-poor soil, they are unlikely to contain helpful amounts of iodine.

In addition to produce grown in iodine-rich soil, the foods that may contain iodine include seafood, dairy products and some kinds of bread. But even if you eat these foods, you may not get enough iodine.

Nearly a hundred years ago, health experts in the United States recommended that iodine be added to something most people sprinkle on their food every day: table salt. Although that helped, it didn’t completely solve the iodine deficiency problem.

#4: Not all salt contains iodine

You can buy iodized table salt, but not every type of salt contains iodine. Grocery stores typically carry both kinds — but unless you know what to look for, you may not be buying iodized salt. To know for sure, check the label; iodine may be listed as iodine, iodide or iodate.

It’s also important to know that you can’t count on salty foods as a source of iodine. Although most Americans get more than enough salt in their diet, most of it comes from processed foods, and the salt in processed foods is generally not iodized.

Related: How Much Salt is Too Much?

#5: To get enough iodine, supplements are recommended — but don’t go overboard

Organizations including the AAP and the American Thyroid Association (ATA) recommend pregnant women take supplemental iodine. In February 2015, ATA made a formal recommendation that women take a daily multivitamin containing 150 micrograms of iodine (in the form of potassium iodide) during preconception, pregnancy and breastfeeding. 

Be careful not to take too much iodine. Excessive amounts can be unsafe to mothers and babies and may cause problems with thyroid function. Avoid kelp supplements, which can contain dangerously high amounts of iodine. Instead, choose prenatal vitamins with 150 micrograms of iodine.

Don’t take additional iodine unless your healthcare provider recommends it. “For most pregnant women, eating a healthful diet and taking a prenatal vitamin — or any multivitamin — is enough,” says Katharine Wenstrom, MD,director of the Division of Maternal-Fetal Medicine and co-director of the Integrated Program for High-Risk Pregnancy at Women & Infants Hospital of Rhode Island, and a professor of obstetrics and gynecology at The Warren Alpert Medical School of Brown University.

It’s good to take a daily prenatal vitamin even if you’re only thinking of becoming pregnant. “The problem is that approximately half of all pregnancies are unplanned, so that by the time a woman knows she’s pregnant, most of the fetal organ systems have already formed,” Wenstrom says.

If you find out you’re pregnant and haven’t been taking a daily prenatal vitamin, start right away, Wenstrom advises. “The most important time for vitamin supplementation is the first eight weeks of pregnancy, when major organs are forming.”

#6: Not all prenatal vitamins contain iodine

You would think that if iodine is so important, it would be in every brand of prenatal vitamin. That’s not the case. To be sure yours contains it, check the label. Even better, talk with your healthcare provider about which prenatal vitamin best suits your nutritional needs.

Alice Lesch Kelly, a health writer based in Boston, is the co-author of "Healthy Mom, Healthy Baby: The Ultimate Pregnancy Guide"(HarperOne, 2013).