About 2,500 children each year in the United States are born with defects of the neural tube, the part of a growing fetus that will become the brain and spinal cord, which can cause severe mental and physical disability or death.

Spina bifida, the most common form of neural tube defect, occurs when the bones of the spine do not completely form around the spinal cord. Anencephaly, another defect, is a fatal condition in which an infant is born missing parts of the brain.

Folic acid, an essential B vitamin necessary for proper cell growth and vital to the development of a baby’s neural tube and central nervous system, is an integral component in preventing birth defects

Women who get enough folic acid have a 50 to 70 percent reduced risk of having a baby with neural tube and other defects, such as cleft lip and palate.

Folic acid is most effective when it is abundant in a woman’s body before she gets pregnant and during the first three months of pregnancy, around the time when the neural tube begins to develop. Neural tube defects occur in the first weeks of fetal development, often before a woman even knows she is pregnant.

But because nearly half of all pregnancies in the US are unplanned, many women are at risk of beginning a pregnancy with a folic acid deficiency.

Because of that, the American Congress of Obstetricians and Gynecologists recommends that all women of child bearing age take a daily multivitamin that contains 400 micrograms,. 4 milligrams, of folic acid, regardless of whether they are planning a pregnancy or not. Taking folic acid before pregnancy ensures that the nutrient is present, even if an unplanned pregnancy occurs or if a pregnancy is not discovered for several weeks.

It’s also a good idea to eat a diet rich in natural sources of folic acid including leafy green vegetables, citrus fruits, and beans, and folic acid-enriched grain products, such as breads, cereals, flours, pastas, and rice. Most women will still need a supplement because it can be difficult to meet the daily requirement through food alone.

Women who have had a child with a neural tube defect or certain other birth defects, are pregnant with twins, have particular medical conditions such as sickle cell disease, or take some forms of medication such as antiseizure medication require 10 times the amount of folic acid recommended for most women.

A daily 4,000 microgram, 4 milligram, folic acid supplement can be prescribed. Women should not consume large amounts of folic acid through regular multivitamins because the quantities of other vitamins and minerals included may be harmful.

For information, the Congress’ patient education pamphlet, Reducing Your Risk of Birth Defects, is available in English and Spanish at www.acog.org/publications/patient_education.

This article was written by Richard N. Waldman, M.D., president of The American Congress of Obstetricians and Gynecologists.