Epidemiologic characteristics of anotia and microtia in California, 1989-1997

Birth Defects Res A Clin Mol Teratol. 2004 Jul;70(7):472-5. doi: 10.1002/bdra.20042.


Background: There is a paucity of epidemiologic information about the external ear malformations anotia and microtia.

Methods: Using data from a large population-based registry, we explored prevalences and maternal/infant characteristics associated with anotia and microtia. Data were derived from the California Birth Defects Monitoring Program, a population-based active surveillance system for collecting information on infants and fetuses with congenital malformations using multiple source ascertainment. Approximately 2.5 million births (live-born and stillborn) occurred during the ascertainment period, 1989-1997. Information on maternal and infant/fetal characteristics was obtained from California birth certificate and fetal death files.

Results: The prevalence of anotia/microtia was 2.50 per 10,000 live births and stillbirths. Isolated cases, i.e., those live births and stillbirths with no other accompanying anomaly diagnoses, revealed a prevalence of 0.63 per 10,000, whereas among nonisolated cases, the prevalence was 1.53 per 10,000 live births and stillbirths. Prevalences of isolated anotia/microtia were substantially higher among U.S.-born Hispanics, foreign-born Hispanics, and Asians compared to non-Hispanic whites, with relative risks ranging from three- to seven-fold. Similar prevalences for maternal race/ethnicity (except for Asians) were observed for live births and stillbirths with nonisolated cases of anotia/microtia, but the magnitude of risks were lower than those observed for isolated cases. Prevalence of nonisolated anotia/microtia was substantially lower among women whose education was 12 years or more.

Conclusions: These data reveal descriptive epidemiologic features of anotia/microtia most notably substantial risks associated with race/ethnic groups and lower maternal education. Additional study for factors associated with these characteristics could reveal clues for the etiology of these ear anomalies.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Age Factors
  • California / epidemiology
  • Ear, External / abnormalities*
  • Female
  • Humans
  • Mothers / education
  • Risk Factors