Epidemiologic characteristics of anotia and microtia in California, 1989-1997.
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.
Shaw
Gary M
GM
March of Dimes Birth Defects Foundation, California Birth Defects Monitoring Program, Berkeley, California, USA. GSH@CBDMP.ORG
Carmichael
Suzan L
SL
Kaidarova
Zhanna
Z
Harris
John A
JA
D000328:Adult; D000367:Age Factors; D002140:California / Q000453:epidemiology; D004431:Ear, External / Q000002:abnormalities*; D005260:Female; D006801:Humans; D009035:Mothers / Q000193:education; D012307:Risk Factors