Oh Baby!

By Peter Galvin, MD

The neural tube and plate are responsible for the development of the cranium (brain and skull) and spine (spinal cord and backbone) in a human fetus. The neural plate completes its formation and closes very early in pregnancy, usually by 26 to 28 days after conception, which is often before a woman even realizes that she is pregnant. Neural tube defects are among the most common congenital malformations, or birth defects, in the U.S., with an estimated 3,000 deliveries affected every year. Many neural tube defects are caused by a mother’s low folate levels. The most common neural tube defects are anencephaly (missing sections of the brain and skull), encephalocele (missing skull sections allow the brain and surrounding tissues [meninges] to protrude), and spina bifida. The CDC estimates that spina bifida occurs in 3.9 per 10,000 live births in the U.S., anencephaly in 2.5 of 10,000 live births, and encephalocele in one per 10,000. Anencephaly and encephalocele usually are responsible for early infant death, and, if the child survives, all three conditions cause significant serious lifetime disability.

Folate refers to vitamin B9, a water-soluble vitamin that occurs in many chemical forms, including naturally in foods such as leafy greens, fruits, nuts, beans, peas, seafood, eggs, dairy products, meat, and poultry. Folic acid is the term applied to the synthetic form of folate found in supplements and added to certain foods. Folic acid supplementation for women in the periconceptional period has been shown to reduce neural tube defects in their offspring. Yet despite folic acid supplementation in many foods, low folate levels remain a concern in the US. Low folate levels can be caused by inadequate dietary intake, poor intestinal absorption, medications that interfere with folic acid function (some anti-seizure medications and methotrexate), and impaired folate metabolism.

Because the neural tube forms and closes so early in pregnancy, the U.S. Preventive Services Task Force (USPSTF) now recommends that not only should all women who are either trying to get pregnant or planning on it take folic acid supplements, it also recommends, since unintended pregnancy does happen, all women of child-bearing age should take folic acid supplements. All pregnancies are at risk for neural tube defects. Certain risk factors confer a higher risk, and they include a personal, partner, or family history of neural tube defects, malabsorption caused by bariatric surgery, the use of certain anti-seizure medications (valproic acid and carbamazepine), the use of methotrexate, and genetic mutations in folate-related enzymes. Pregestational diabetes and obesity have been associated with an increased risk and certain ethnic groups such as First Nation people in Canada and Hispanic women in California are at increased risk.

Numerous studies have shown the benefit of taking folic acid supplements before and during pregnancy to prevent neural tube defects, including several studies that showed a statistically significant reduction of autism in children born to women on folic acid supplementation. In addition, studies have shown that there is no evidence of any harm, both to mothers and their children, from folic acid supplements. The USPSTF recommends folic acid supplementation at 400 to 800 micrograms per day, a dosage found in most prenatal vitamins. Folic acid supplements should be taken at least through the first trimester.

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