Birth prevalence, mutation rate, sex ratio, parents' age, and ethnicity in Apert syndrome.

Apert syndrome was studied to determine birth prevalence, mutation rate, sex ratio, parents' age, and ethnicity among 2,493,331 live births registered in the California Birth Defects Monitoring Program (CBDMP) from 1983 through 1993; 31 affected infants were identified. The sample was completed with an additional 22 cases from the Center for Craniofacial Anomalies (CCA), University of California, San Francisco, for a total of 53 affected children. Birth prevalence, calculated from the CBDMP subsample, was 12.4 cases per million live births (confidence interval [CI] 8.6,17.9). The calculated mutation rate was 6.2 x 10(-6) per gene per generation. Asians had the highest prevalence (22.3 per million live births; CI 7.1,61.3) and Hispanics the lowest (7.6 per million, CI 3.3-16.4). In the large population-based CBDMP subsample, there was an almost equal number of affected males and females, (sex ratio 0.94) but in the clinical CCA subsample, there were more affected females (sex ratio 0.79). For all cases, the mean age of mothers was 28.9+/-6.0 years, and of fathers was 34.1+/-6.2 years. Almost half of fathers were older than 35 years when the child was born; for more than 20% of cases, both parents were older than 35 years. These findings may support the view that point mutations appear to be more commonly associated with paternal than with maternal alleles. Representing the largest systematically ascertained population-based study of Apert syndrome to date, they provide a reliable basis for genetic counseling and decision-making, and for focused research to define the cause of this syndrome.