Background

The goal of this systematic review was to determine whether dietary patterns are associated with risk of congenital anomalies (neural tube defects, congenital heart defects, cleft lip and palate). Dietary patterns were defined as the quantities, proportions, variety or combination of different foods, drinks and nutrients in diets, and the frequency with which they are habitually consumed.

Conclusion statement

Limited evidence suggests that healthy maternal dietary patterns during the preconception period that are higher in vegetables, fruits and grains; lower in red and processed meats; and low in sweets were associated with lower risk of developing of neural tube defects, particularly among women who do not take folic acid supplements. Whereas some dietary patterns were associated with lower risk of developing anencephaly, others were associated with lower risk of developing spina bifida. Evidence is insufficient to determine an association between maternal dietary patterns and congenital heart defects or cleft lip and palate. All studies were consistent in demonstrating that folic acid supplementation periconceptionally was associated with a decreased risk of having a child with a birth defect (e.g., neural tube defects, congenital heart defects, and cleft lip and palate).

2015 DGAC Grade:

• Neural tube defects: Limited
• Congenital heart defects: Not assignable
• Cleft lip/palate: Not assignable

Methods

Literature searches were conducted using PubMed, Embase, Navigator (BIOSIS, CAB Abstracts and Food Science and Technology Abstracts) and Cochrane databases to identify studies that evaluated the association between dietary patterns and risk of congenital anomalies. Studies that met the following criteria were included in the review: randomized controlled trials (RCTs), non-randomized controlled trials, prospective cohort studies or casecontrol studies; adolescent girls and women capable of becoming pregnant and who were healthy or at elevated chronic disease risk; subjects from countries with high or very high human development (2012 Human Development Index); and published in English in peerreviewed journals. The date range was January 1980 to April 2014. The intervention or exposure was adherence to a dietary pattern (e.g., a priori patterns, data-driven patterns, reduced rank regression (RRR) or patterns derived from other methods, and a description of the dietary pattern(s) (i.e., foods and beverages) consumed by subjects was provided. The outcomes were incidence of neural tube defects, congenital heart defects, cleft lip, and cleft Systematic Reviews of the Dietary Patterns, Food and Nutrients Subcommittee, 2015 DGAC 153 Archived from www.NEL.gov on March 21, 2017 palate.

Data from each included article were extracted, and risk of bias was assessed. The evidence was qualitatively synthesized, a conclusion statement was developed and the strength of the evidence (grade) was assessed using preestablished criteria including evaluation of the quality and risk of bias, quantity, consistency, magnitude of effect and generalizability of available evidence.

Findings

• This series of systematic reviews included five case-control studies (using data from three cohorts) published since 1980 that examined the relationship between maternal dietary patterns and congenital anomalies in infants. Three articles examined neural tube defects, two articles examined congenital heart defects and two articles examined orofacial clefts
• Although all five case-control studies reported significant associations between dietary patterns and risk of congenital anomalies in women not taking folic acid supplementation, the variability of dietary patterns methodology used and composition of dietary patterns identified made it difficult to draw conclusions
• All studies were consistent in finding that folate delivered periconceptionally in food or as a supplement as a key nutrient was associated with lower risk of developing congenital anomalies. It should be noted that some of the included studies were conducted in countries with mandatory folate fortification, while others were from countries that prohibit such fortification.

Limitations

The ability to draw strong conclusions was limited by the following issues:

• There were relatively few studies available to address this question, and those available used different dietary patterns assessment techniques.