We compared the birth prevalence of anencephaly and spina bifida among several racial/ethnic groups in the United States. Using birth data for the years 1989 to 1991 (N = 10,225,502), we estimated logistic regression models that included variables controlling for maternal age and race/ethnicity for anencephaly and spina bifida. The overall birth prevalence of anencephaly was 1.81 (95% C.I., 1.72 - 1.89) and that of spina bifida 2.67 (95% C.I., 2.57 - 2.77) per 10,000 live births. Results of logistic models for anencephaly showed that infants born to Mexican mothers had a 2-fold increase [Adjusted Odds Ratio (OR): 2.06, 95% C.I., 1.83 - 2.33], and infants born to Puerto Rican mothers a 50% increase [Adjusted OR: 1.53, 95% C.I., 1.03 - 2.28] in prevalence of anencephaly as compared with infants born to Non-Hispanic White mothers. On the other hand, infants born to African American mothers had a birth prevalence of anencephaly that was similar to that of Whites [Adjusted OR for African Americans: 0.96, 95% C.I., 0.84 - 1.11]. Results of logistic models for spina bifida showed that infants born to African American mothers had a 38% lower prevalence of spina bifida at birth [Adjusted OR: 0.62, 95% C.I., 0.55 - 0.70] as compared with Non-Hispanic Whites. Infants born to Mexican mothers had a 24% lower [Adjusted OR: 0.76, 95% C.I., 0.67 - 0.87) and infants born to other Hispanic mothers with the exception of Puerto Ricans a 40% lower [Adjusted OR: 0.60, 95% C.I., 0.47 - 0.78] prevalence of spina bifida at birth as compared with Non-Hispanic Whites. Finally, results of logistic models did not reveal any obvious effect of maternal age on the risks for anencephaly or spina bifida.

Conclusions: 1. Infants born to Mexican mothers had a 2-fold increase in the risk for anencephaly but a 24% lower risk for spina bifida as compared with Non-Hispanic Whites. 2. Infants born to African American had a 38% and Hispanic mothers other than Puerto Ricans a 40% lower risk of spina bifida. 3. Infants born to Puerto Rican mothers had a 50% higher risk for anencephaly.