The effects of zero population growth on the incidence of cleft lip and palate in Western Australia.

Abstract

A total of 613 cases of cleft lip, cleft palate, and combinations of both (CLP(P)) has been ascertained in the period from 1958 to 1975 in Western Australia. Near-total ascertainment of cases during this period was obtained from multiple sources. There has been a significant decline in the total incidence and the cleft lip and palate (CLP) incidence in males. The hypothesis is presented that these changes are linked to the changing fertility pattern throughout Australia (as technological improvements are made in the simplicity and efficacy of birth control), and abortion (as social attitudes change); and as the birthrate drops towards zero population growth (ZPG). The paper presents two critical observations: (i) the link between CLP(P) incidence, and demographic changes; (ii) in differing behaviour of cleft lip (CL) and CLP, which were previously regarded as linked conditions.