Because folate deficiency in pregnant women has been associated with an increased risk of neural tube defects, including anencephaly and spina bifida, it is recommended that all women take folic acid supplements during pregnancy.  In addition, the Food and Drug Administration (FDA) has required (since 1998) the addition of folic acid to many enriched breads and cereals in order to increase the amount of folic acid in our diets.  Since this FDA recommendation was put into place, there has been about a 65% reduction in the prevalence of neural tube defects in the general population.

While pregnant women are told to avoid extreme diets or weight reduction during pregnancy, many women now adhere to low carbohydrate and gluten-free diets on a regular basis and plan to maintain these dietary habits during pregnancy.  The concern here is that women who adhere to low carbohydrate diets would not benefit from the folate added to grain products, such as wheat flour, rice, and pasta.  And for women who have celiac disease or gluten sensitivity, a recent study found that gluten-free breads, cereals, and pasta are typically not fortified with folic acid.  

Without this contribution of folic acid fortified foods in their diets, would these women be at greater risk for having a child with a neural tube defect?

In order to answer this question, researchers examined the association between carbohydrate intake and neural tube defects, analyzing data from the National Birth Defects Prevention Study which included 1,740 mothers of infants, stillbirths, or terminations with anencephaly or spina bifida (cases), and 9,545 mothers of live born infants without a birth defect (controls). Using a food frequency questionnaire, women provided information regarding carbohydrate and folic acid intake before conception.  Restricted carbohydrate intake was defined as ? 5th percentile.

The researchers found that women with restricted carbohydrate intake were slightly more likely to have an infant with a neural tube defect after accounting for potential variables, including use of prenatal vitamins (AOR?=?1.41, 95% CI: 1.11, 1.79).  While this is not a huge increase in risk, it is statistically significant and raises concerns about women’s dietary habits during pregnancy.  

Probably the most concerning finding in this study is that only 30% took prenatal vitamins on a regular basis during pregnancy. Presumably supplementation with folic acid would help to replete folate stores in women on low carbohydrate diets; however, we cannot rule out the possibility that other factors associated with a low carb diet may confer some degree of risk to the developing fetus.  

Based on these findings, the authors recommend that women who are pregnant or planning to become pregnant may want to avoid diets that reduce or eliminate carbohydrates, as they could increase the risk of having a child with a neural tube defect.  And we continue to recommend that all women of reproductive ago use folic acid supplements on a regular basis.

Ruta Nonacs, MD PhD

 

Desrosiers TA, Siega-Riz AM, Mosley BS, Meyer RE. Low carbohydrate diets may increase risk of neural tube defects. National Birth Defects Prevention Study.  Birth Defects Res. 2018 Jan 25.