Studies in spina bifida cystica. III. Seasonal variation in the frequency of spina bifida births.

This communication continues the analysis of data accumulated from a series of cases of spina bifida cystica observed during the years 1949 to 1958. In earlier papers, attention was drawn to the magnitude of the problem presented by these cases and to the amount of medical and surgical care which they require (Doran and Guthkelch, 1961) and to certain complications which need consideration in planning the surgical repair of the spinal defect (Guthkelch, 1962). Other workers (McKeown and Record, 195 1; Edwards, 1958) have looked for a seasonal incidence in spina bifida births but have failed to find one. But the same workers have demonstrated clearly that there is a considerable seasonal variation in the frequency of anencephalus births, the winter incidence of which is about a third as great again as the summer incidence, and there is every reason to suppose that anencephalus and spina bifida are two aspects of a fundamentally similar disorder, that is to say a failure of closure of the primitive neural plate during early embryonic life. It is well known that anencephalus and the grosser forms of spina bifida often occur in the same individual and indeed complete craniorachischisis is not a rare human malformation. Warkany (1960) has drawn attention to the fundamental similarity of the pathological changes which are seen in experimental spina bifida and anencephaly in the rat. For this reason, it seemed desirable to search our own material and that previously published, in order to see whether any seasonal trend could be observed in the incidence of spina bifida similar to that already established for anencephalus. McKeown and Record (1951) set out the monthly figures for spina bifida still-births in Scotland between 1939 and 1946 in detail (Table I). They suggested that the incidence of spina bifida still-births per thousand births for each month of the year TABLE I