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Articles & Key Findings

Key Findings: Blood Folate Concentrations and Risk of Neural Tube Defect-Affected Pregnancies: Where Does the United States Stand?

Pregnant female choosing between broccoli in glass bowl and vitamins.

Birth Defects Research Part A has published a new study that looked at the amount of folate in the blood (“blood folate concentrations”) among women in the United States in relation to their risk of having a baby affected by a neural tube defect. Blood folate concentrations refer to the amount of folate (a B vitamin) found in blood. Blood folate concentrations among women have been shown to predict the risk in populations of having pregnancies affected by neural tube defects.

In this study, CDC researchers found that more than 3 out of 4 (77.2%) women in the United States had blood folate concentrations at levels that would optimally prevent pregnancies affected by neural tube defects. These findings are useful for identifying population subgroups at greater risk for pregnancies affected by neural tube defects and targeting the ways to better prevent neural tube defects in those groups. You can read the article’s abstract here.

What are neural tube defects?

  • Neural tube defects are serious birth defects of the brain and spine.
  • The two most common neural tube defects are spina bifida (affects the spine) and anencephaly (affects the brain).
  • Neural tube defects happen during the first month of pregnancy.

What is folate?

  • Folate is a B vitamin that is present naturally in foods. Folic acid is a synthetic form of folate that is added to vitamins and some foods.
  • Many, but not all, neural tube defects can be prevented by consuming enough folic acid daily. These birth defects are called folate-sensitive neural tube defects.
  • It is important that women of reproductive age consume 400 mcg of folic acid daily by taking a daily vitamin with folic acid in it, by eating food that is fortified with folic acid (such as some breakfast cereals and other cereal grain products), or both, in addition to eating a diet rich in natural folate.
  • If a woman has enough folate in her blood before and during early pregnancy, from synthetic and natural sources, it can help prevent neural tube defects.

About This Study

We already know that…

  • Blood folate concentrations can predict the risk of neural tube defects in populations.
  • Mandatory folic acid fortification has increased blood folate concentrations and decreased the prevalence of neural tube defects in the United States.
    • Blood folate concentrations for women aged 15-44 years increased 54.5% between 1988-1994 (before fortification) and 1999-2010 (after fortification).
    • The rate of neural tube defects has declined an estimated 35% since fortification.

Yet, approximately 2,500 to 3,000 pregnancies in the U.S. are affected by a neural tube defect every year.

This study provides information on the population of U.S. women of childbearing age with blood folate concentrations that are below the level needed for optimal prevention of neural tube defects (a red blood cell folate concentration less than or equal to 906 nmol/L).

This study used data from the National Health and Nutrition Examination Survey (NHANES), which collects data from a nationally representative sample of the U.S. population. NHANES data are collected in 2-year phases. This study used data from 2007-2008, 2009-2010, and 2011-2012. The analysis focused on nonpregnant women of childbearing age, which was defined as women aged 12 to 49 years.

Main Findings from This Study

This study found that more than 3 out of 4 (77.2%) women in the United States had blood folate concentrations at levels that would optimally prevent pregnancies affected by neural tube defects. Although nearly a quarter of women of childbearing age (22.8%) did not have optimal blood folate concentrations to prevent neural tube defects, their concentrations were primarily in the elevated risk category (9-14 neural tube defects per 10,000 live births) rather than the highest risk category (more than 14 neural tube defects per 10,000 live births).

Prevention policies and programs should focus on population subgroups identified as having a higher predicted risk. Among U.S women in this study, those who did not have optimal blood folate concentrations were more likely:

What’s next?

Further research is needed to determine the best strategies to increase blood folate concentrations among population subgroups with higher predicted risk for pregnancies affected by neural tube defects.

As a reminder for clinicians, all women of childbearing age need 400 micrograms (mcg) of folic acid daily and healthcare providers are a highly trusted source for this information. It is important to advise patients to get enough synthetic folic acid daily from fortified foods or supplements, or both, and to consume a balanced, healthy diet of folate-rich food.

Paper Reference

Tinker SC, Hamner HC, Qi YP, Crider KS. U.S. Women of Childbearing Age Who Are at Possible Increased Risk of a Neural Tube Defect-Affected Pregnancy Due to Suboptimal Red Blood Cell Folate Concentrations, National Health and Nutrition Examination Survey 2007 to 2012. Birth Defects Research Part A: 2015.

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