Background: Few studies have investigated the epidemiologic features of clinically defined subgroups of anotia/microtia.
Methods: Data on cases of anotia and/or microtia among 1999-2005 deliveries were obtained from the Texas Birth Defects Registry, a population-based active surveillance system. We determined crude and adjusted associations between selected factors and seven clinical subgroups of anotia/microtia.
Results: In total, 742 cases were diagnosed with anotia and/or microtia, corresponding to a prevalence of 2.86 per 10,000 live births. Of those, 45% had no other major birth defect ("isolated"), 77% were unilateral, and 22% bilateral. Anotia alone made up 6%, whereas microtia made up 94%. Birth prevalence was higher with increasing maternal age and among Mexico-born Hispanics. Compared to white mothers, Hispanic mothers were two-to-three times more likely to have infants with all but the syndromic and bilateral groups (adjusted prevalence ratios [aPRs] = 2.05-2.61). Non-Hispanic blacks had significantly lower risk for total anotia/microtia, and for the isolated, unilateral, and microtia subgroups (aPRs = 0.42-0.64). Less educated mothers were three-to-four times more likely to have children with anotia (aPRs = 2.98 for less than high school, 3.97 for high school graduates). Males were more likely to be born with total anotia/microtia and with syndromic, unilateral, and microtia subtypes (aPRs = 1.27-1.41).
Conclusions: In Texas, most anotia/microtia cases were in the unilateral and microtia groups, and 45% were isolated. Several clinical subgroups exhibited higher prevalence in males and among older mothers. Relative to whites, blacks were at lower risk and Hispanics (especially Mexico-born mothers) were at higher risk for selected types of anotia/microtia.