The United States Preventive Services Task Force still says that all women planning to have a child or capable of having one take 0.4 to 0.8 milligrams of folic acid in a supplement daily, according to a new statement from the government-backed panel.

Folic acid, found naturally in many fruits and vegetables like leafy greens and added to some fortified cereals, helps prevent neural tube defects in a developing fetus.

Neural tube defects include spina bifida, where the spinal cord doesn't close completely, and anencephaly, where parts of the brain are missing.

They typically happen in the first month of pregnancy.

"People don't really understand the importance of getting folic acid very early, oftentimes before they realize they are pregnant," said Task Force member Dr. Alex R. Kemper, professor of pediatrics at Duke University Medical School.

The USPSTF issued the same recommendation in 2009, but most women still do not get the recommended 0.4 mg of folic acid daily. A 2007-2012 national survey found that only 29 percent of women of childbearing age were taking a folic acid supplement - and half of those were taking less than the recommended dose.

"The key things to know are that most women don't get enough folic acid normally in their diet, also some available supplements don't have the recommended amount," Kemper told Reuters Health by phone.

Neural tube defects are rare, affecting about seven in every 10,000 live births, a decrease from more than 10 per 10,000 live births in 1998 when the U.S. Food and Drug Administration implemented food fortification laws.

Women with a personal or family history of neural tube defects are at much higher risk of having a child with a neural tube defect. Taking a folic acid supplement from one month before conception to two or three months of pregnancy can greatly reduce these risks, according to the statement.

A bottle of 250 tablets of 0.4 mg folic acid costs roughly five dollars from stores like Target or Walmart.

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Women of childbearing age and their primary care providers should be aware of this recommendation, Kemper said.

Women who find out they are pregnant but who haven't been taking the supplements should go ahead and start taking them as soon as they find out, he said.

The benefits are clear and there are no known significant harms of folic acid supplements, he said.