Are encephaloceles neural tube defects?
OBJECTIVE
Encephalocele is classified as a neural tube defect, but questions have been raised regarding whether its epidemiological characteristics are similar to those of other neural tube defects.


METHODS
We compared characteristics of temporal trends in, and the impact of folic acid grain fortification on, the prevalence of encephalocele, spina bifida, and anencephaly using data from the Metropolitan Atlanta Congenital Defects Program, a population-based birth defects surveillance system. Prevalences of encephalocele, spina bifida, and anencephaly were compared by maternal age, gender, race, birth weight, ascertainment period (1968-1981, 1982-1993, or 1994-2002), and fortification period (1994-1996 [prefortification] and 1998-2002 [postfortification]) using prevalence ratios with 95% confidence intervals. Temporal trends were assessed using Poisson and negative binomial regression models.


RESULTS
Prevalence rates of encephalocele (n = 167), spina bifida (n = 650), and anencephaly (n = 431) were 1.4, 5.5, and 3.7 per 10 000 live births, respectively. Encephalocele was similar to anencephaly in showing an increased prevalence among girls and multiple gestation pregnancies and to spina bifida and anencephaly in an annual prevalence decrease between 1968 and 2002 (-1.2% for encephalocele, -4.2% for spina bifida, and -3.6% for anencephaly). With fortification, prevalence decreased for spina bifida but not significantly for encephalocele or anencephaly.


CONCLUSIONS
Encephalocele shows more similarities to spina bifida or anencephaly than it shows differences with respect to characteristics, temporal trend, and impact of fortification. Additional studies should be done to explore the etiologic heterogeneity of encephalocele using better markers of folate status and a wider range of risk factors.
Rowland
Courtney A
CA
National Center on Birth Defects and Developmental Disabilities, Centers for Disease Control and Prevention, 1600 Clifton Rd, Mailstop E-86, Atlanta, Georgia 30333, USA.
Correa
Adolfo
A
Cragan
Janet D
JD
Alverson
Clinton J
CJ
D000293:Adolescent; D000328:Adult; D000757:Anencephaly / Q000145:classification / Q000453:epidemiology / Q000517:prevention & control; D004677:Encephalocele / Q000145:classification / Q000453:epidemiology* / Q000517:prevention & control*; D005260:Female; D005492:Folic Acid / Q000627:therapeutic use*; D005527:Food, Fortified; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008423:Maternal Age; D009436:Neural Tube Defects / Q000145:classification / Q000453:epidemiology* / Q000517:prevention & control*; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D012737:Sex Factors
D005492:Folic Acid