Spina bifida subtypes and sub-phenotypes by maternal race/ethnicity in the National Birth Defects Prevention Study

Spina bifida refers to a collection of neural tube defects, including myelomeningocele, meningocele, and myelocele (SB(M) ), as well as lipomyelomeningocele and lipomeningocele (SB(L) ). Maternal race/ethnicity has been associated with an increased risk for spina bifida among offspring. To better understand this relationship, we evaluated different spina bifida subtypes (SB(M) vs. SB(L) ) and sub-phenotypes (anatomic level or presence of additional malformations) by maternal race/ethnicity using data from the National Birth Defects Prevention Study. This study is a large, multisite, population-based study of nonsyndromic birth defects. Prevalence estimates were obtained using data from spina bifida cases (live births, fetal deaths, and elective terminations) and total live births in the study regions. From October 1997 through December 2005, 1,046 infants/fetuses with spina bifida were delivered, yielding a prevalence of 3.06 per 10,000 live births. Differences in the prevalences of SB(M) vs. SB(L) , isolated versus non-isolated SB(M) , and lesion level in isolated SB(M) among case offspring were observed by maternal race/ethnicity. Compared to non-Hispanic (NH) White mothers, offspring of Hispanic mothers had higher prevalences of each subtype and most sub-phenotypes, while offspring of NH Black mothers generally had lower prevalences. Furthermore, differences in race/ethnicity among those with isolated SB(M) were more pronounced by sex. For instance, among male offspring, the prevalence of isolated SB(M) was significantly higher for those with Hispanic mothers compared to NH White mothers [prevalence ratio (PR): 1.55, 95% confidence interval: 1.23-1.95]. These findings provide evidence that certain spina bifida subtypes and sub-phenotypes may be etiologically distinct.