Anencephalus, Spina Bifida, and Hydrocephalus: Incidence Related to Sex, Race, and Season of Birth, and Incidence in Siblings

Abstract

For the congenital malformations, as for many other non-communicable diseases and defects, the collection of epidemiological knowledge based on statistical procedures is just beginning. A compre hensive investigation of the incidence of malforma tions of the central nervous system in Birmingham, England, and the relationship of these malformations to certain epidemiological variables, has recently been reported by Record and McKeown (1949; 1950a,b; 1951) and McKeown and Record (1951). With the object of determining the applicability of these authors' results to areas other than England and Wales, a somewhat similar, retrospective investigation was undertaken in Rhode Island, U.S.A. This communication describes the findings of this investigation, with the exception of data relevant to the association with maternal age and parity, which is reported separately (Ingalls, Pugh, and MacMahon, 1953). Material The study is concerned with all cases of anencephalus, spina bifida, encephalocele, and hydrocephalus born in the five largest maternity units in the state of Rhode Island during the years 1936-52. For the years 1936-49 births in these hospitals constituted 67 per cent, of all births in the state. For the years 1950-52, the 1949 level of 74-4 per cent, was almost certainly maintained, but vital statistics are not yet available. Information about the total population of births was obtained from monthly hospital reports and from a sample group assembled by taking every hundredth name