Major central nervous system malformations in South Wales. II. Pregnancy factors, seasonal variation, and social class effects.

Abstract

This is a report on part of a survey which began in 1960 in the Vale of Glamorgan and the mining valleys of Monmouthshire and Glamorgan east of the Neath Valley to investigate genetic and the environmental factors affecting the incidence of the major central nervous system (neural tube) malfor- mations. Details of the survey area, total birth population, ascertainment methods, incidence, and the possible relation of geographical factors to the wide local variations observed have already been published (Laurence, Carter, and David, 1968). The genetic aspects of the survey (Carter, Laurence, and David, 1968) and the natural history of spina bifida (Laurence, Tew, David, and Carter, 1968) are the subject of other publications. We here present and assess the significance of some of the pregnancy, seasonal, and social factors.