Congenital anomalies of the central nervous system incidence in British Columbia, 1952-72.

The records of an ongoing health surveillance registry that utilizes multiple sources of ascertainment were used to study the incidence rates of congenital malformations of the central nervous system in children born in British Columbia during the period 1952-72. No overall increase in incidence rate of these anomalies was detected over the study period and the total frequency ascertained was three per thousand births. For anencephaly, spina bifida, hydrocephaly, and other CNS anomalies, the estimated incidence rates per 1,000 births are 0.6, 0.8, 1.0 and 0.5 respectively. A greater incidence rate or neural tube closure defects was found in females than in males and this difference was most marked amongst the stillbirths. The data indicate that multiple sources of ascertainment and follow-up of children beyond one year after birth are necessary for adequate reporting even for these sorts of defects which have generally been though to be readily recognized at or shortly after birth.