THE EPIDEMIOLOGY OF ANOTIA AND MICROTIA

We studied a large data set from three registries of congenital malfor mations (central-east France, Sweden, and California), a total of 954 cases, known chromosome anomalies excluded. The prevalence at birth va ried significantly between programmes, probably to a large extent beca use of different ascertainment and inclusion criteria, from 0.76 per 1 0 000 births in the French programme to 2.35 in the Swedish. Within th e California programme, there is a racial variability in prevalence wi th lower values among whites (and probably blacks) than in Hispanics a nd Asians. Also the proportion of anotia and microtia varies between r aces with the lowest proportion of anotia in whites. Anotia and microt ia are equally often associated with other malformations and show othe r similar epidemiological characteristics. In unilateral cases, the ri ght side is more frequently malformed than the left side, especially w hen the ear malformation is isolated. There is a male excess, most pro nounced in isolated forms. Among associated malformations, facial clef ts and cardiac defects are the most common ones (each about 30% of inf ants with associated malformations), followed by anophthalmia or micro phthalmia (14%), limb reduction defects or severe renal malformations (11%), and holoprosencephaly (7%). There is a maternal parity effect s een, an increased risk at parity 4+ (standardised for maternal age), m ore pronounced for anotia than microtia.