The epidemiology of anotia and microtia.

We studied a large data set from three registries of congenital malformations (central-east France, Sweden, and California), a total of 954 cases, known chromosome anomalies excluded. The prevalence at birth varied significantly between programmes, probably to a large extent because of different ascertainment and inclusion criteria, from 0.76 per 10,000 births in the French programme to 2.35 in the Swedish. Within the California programme, there is a racial variability in prevalence with lower values among whites (and probably blacks) than in Hispanics and Asians. Also the proportion of anotia and microtia varies between races with the lowest proportion of anotia in whites. Anotia and microtia are equally often associated with other malformations and show other similar epidemiological characteristics. In unilateral cases, the right side is more frequently malformed than the left side, especially when the ear malformation is isolated. There is a male excess, most pronounced in isolated forms. Among associated malformations, facial clefts and cardiac defects are the most common ones (each about 30% of infants with associated malformations), followed by anophthalmia or microphthalmia (14%), limb reduction defects or severe renal malformations (11%), and holoprosencephaly (7%). There is a maternal parity effect seen, an increased risk at parity 4+ (standardised for maternal age), more pronounced for anotia than microtia.