Factors associated with anencephalus and spina bifida in Belfast.

A high incidence of major malformations of the central nervous system has been reported from both Northern Ireland (Stevenson, Johnston, Stewart, and Golding, 1966) and the Irish Republic (Coffey and Jessop, 1957). These studies, however, were based on hospital births only, leaving some doubt as to whether these high frequencies are real or partly due to preselection of such cases for management in specialist obstetric units. Up to 1968, only one Irish community study based on complete ascertainment of the major central nervous system malformations occurring in a defined population-Belfast during one year, 1957-had been conducted (Stevenson and Warnock, 1959). Thus, further investigations were initiated in Northern Ireland, and to date some of the findings of a survey into anencephalus in Belfast have been presented (Elwood and Warnock, 1969; Elwood, 1970a; Elwood and MacKenzie, 1971). The current study is the first report of a multidisciplinary investigation into spina bifida in Belfast and also includes some considerations of anencephalus not previously reported.