Epidemiological aspects of Mendelian syndromes in a Spanish population sample: II. Autosomal recessive malformation syndromes.

From April, 1976, to December, 1988, the Spanish Collaborative Study of Congenital Malformations (ECEMC) monitored a total population of 710,815 liveborn infants in 16 of 17 Spanish Regions and identified 14,439 (2.0%) with congenital defects. Among the malformed children, we identified 73 with well recognized autosomal recessive syndromes, for an overall prevalence rate of 10.3 per 100,000 livebirths and a total carrier frequency of 1/49. Considering the Spanish Regions (Comunidades Autónomas), we analyzed the geographical distributions of these syndromes that were homogeneous. We studied the place of birth of the grandparents to determine the distribution of the gene as well as the gene flow.