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Interpreting changes in the epidemiology of anencephaly and spina bifida following folic acid fortification of the U.S. grain supply in the setting of long-term trends, Atlanta, Georgia, 1968–2003

Authors

  • Lilah M. Besser,

    1. National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia
    Current affiliation:
    1. 51 Grapevine Trail, Durham, NC 27707
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  • Laura J. Williams,

    1. National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia
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  • Janet D. Cragan

    Corresponding author
    1. National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, Atlanta, Georgia
    • Centers for Disease Control and Prevention, Mailstop E86, 1600 Clifton Road NE, Atlanta, GA 30333
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  • This article is a US Government work and, as such, is in the public domain in the United States of America.

    Presented at the International Clearinghouse for Birth Defects Monitoring Systems (ICBDMS)/National Birth Defects Prevention Network (NBDPN) Collaborative Meeting, September 20, 2002, Atlanta, Georgia, and at the annual meeting of the Society for Pediatric and Perinatal Epidemiologic Research, June 20–21, 2006, Seattle, Washington.

    The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.

Abstract

BACKGROUND:

The prevalence of anencephaly (AN) and spina bifida (SB) was declining long before fortification of enriched grains in the U.S. with folic acid. We examined whether changes in these defects surrounding fortification could be distinguished from preexisting trends.

METHODS:

We used data from the Metropolitan Atlanta Congenital Defects Program to identify three ascertainment periods: Period 1 (1968–1981), prenatal diagnoses rarely made; Period 2 (1981–1993), prenatal diagnoses made but not ascertained; Period 3 (1994–2003), prenatal diagnoses ascertained. We compared the annual percent change (APC) in AN and SB for each period using Poisson regression, then compared prevalences during each period for categories of pregnancy outcome, sex, race, gravidity, and maternal age.

RESULTS:

The prevalence of AN (N = 434) and SB (N = 663) declined during 1968–2003. The APCs in Periods 1, 2, and 3, respectively, were −6.9%, −2.9%, and −6.8% for AN, and −7.1%, −7.0%, and −6.2% for SB; 95% confidence intervals around the APCs for Periods 2 and 3 overlapped for both defects. Prevalence ratios (PRs) for females relative to males decreased for AN (2.3 in Period 1; 1.2 in Period 3); PRs for whites relative to blacks or African Americans decreased for both AN (2.7 in Period 1; 1.2 in Period 3) and SB (2.5 in Period 1; 1.1 in Period 3).

CONCLUSIONS:

Our analysis suggests that changes in AN and SB surrounding folic acid fortification (Period 3) could be part of preexisting trends. This must be considered when evaluating prevention efforts. Birth Defects Research (Part A) 79:730–736, 2007. © 2007 Wiley-Liss, Inc.

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