Women with high-quality diets during the year before pregnancy were at lower risk than were those with poor diets for delivering a baby with orofacial clefts or neural tube defects, according to a study published online Oct. 3 in Archives of Pediatrics and Adolescent Medicine.
This finding, from an analysis of data in the ongoing National Birth Defects Prevention Study (NBDPS), is "notable" because previous analyses of the same data, "which assessed single-nutrient intakes in isolation, had not been informative.
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Women who followed high-quality diets a year before pregnancy were at lower risk for delivering a baby with orofacial clefts or neural tube defects, compared with women with poor diets.
"In particular, maternal intake of folic acid–containing vitamin/mineral supplements was not associated in the NBDPS with a reduced risk of neural tube defects, and findings for dietary folate were inconsistent" in these previous analyses, said Suzan L. Carmichael, Ph.D., of Stanford (Calif.) University and her associates.
"[Our] findings suggest that overall diet quality is more predictive of birth defect risk than intake of single nutrients," they noted.
Dr. Carmichael and her colleagues developed two indexes of dietary quality, one modeled after the Mediterranean Diet Score and the second after the Diet Quality Index for Pregnancy. They then assessed how each of these indexes performed in predicting risk for isolated (nonsyndromic) neural tube defects and orofacial clefts using data on 9,558 pregnancies in the NBDPS.
The NBDPS is an ongoing multistate, population-based case-control study of well-defined birth defects. For this analysis, the researchers assessed 3,411 pregnancies involving isolated neural tube defects (936) or orofacial clefts (2,475), and 6,147 pregnancies that served as controls. All the deliveries occurred between 1997 and 2005.
For both indexes of dietary quality, "we observed reduced birth defects risks associated with higher dietary quality scores. That is, after adjusting for all covariates, increasing diet quality based on either index was associated with reduced risk of each birth defect studied," the researchers said (Arch. Pediatr. Adolesc. Med. 2011 [doi:10.1001/archpediatrics.2011.185]).
"The strongest associations were observed for anencephaly," they added.
The findings were similar in further analyses of important subgroups of patients, including an assessment restricted to women who took vitamin/mineral supplements.
These results likely are generalizable to other women "because of [our] study’s population-based design, active case ascertainment, and the racial/ethnic, geographic, and socioeconomic diversity" of the subjects.
"Although the focus on folic acid has enabled substantial reductions in the prevalence of neural tube defects and perhaps other birth defects, the population burden of birth defects remains extensive. If increased dietary quality can indeed have a greater impact than individual nutrients, appropriate public health messages may need to be developed that convey this broader perspective," Dr. Carmichael and her associates said.
In an editorial accompanying this report, David R. Jacobs Jr., Ph.D., and his associates said, "The lesson from the article by Carmichael et al. is an important one: People, including women of childbearing age, should eat good food."
"A nutrient [supplement] may correct a deficiency condition but not necessarily be of benefit at higher doses in well-nourished people," they added (Arch. Pediatr. Adolesc. Med. 2011 [doi:10.1001/archpediatrics.2011.184]).
"Reduction of neural tube defects may be achievable by diet alone, at the same time reducing potential risk for other chronic diseases in the rest of the population," said Dr. Jacobs and his associates in the division of epidemiology and community health at the University of Minnesota School of Public Health, Minneapolis.
This study was supported in part by the National Institutes of Health and the Centers for Disease Control and Prevention. Dr. Carmichael and her associates and Dr. Jacobs and his associates reported no relevant financial disclosures.