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

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Abstract
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. Birth Defects Research (Part A), 2004.