A DECLINE IN THE INCIDENCE OF CLEFT LIP AND PALATE IN WESTERN AUSTRALIA, 1963 TO 1972

Abstract

A total of 332 cases of cleft lip (CL), cleft palate (CP) and cleft lip and palate (CLP) were ascertained in the 10-year period 1963–1972. It is considered that these cases can be related directly to the State birthrate and that they represent a total incidence survey. The survey showed a relatively high average incidence rate (1–73 cases per 1,000 births). Stillbirths cannot be fully investigated, but there is some evidence to indicate that one-quarter of the total with these defects are stillborn or die before operation. There is positive evidence of a decline in the incidence in this particular period; a statistically significant regression has been demonstrated for male CLP and total CLP. The occurrence of CL appears to be different from CLP. The ratio of the three conditions, CL (25·3%), CP (39·2%) and CLP (35·5%), differs from that reported in other surveys. There appears to be an alternating pattern in the occurrence of male and female CP on a monthly and yearly analysis.