Spina bifida and hydrocephalus: a population study over a 35-year period.

The records of the B.C. Health Surveillance Registry were used to analyze all live births with spina bifida and hydrocephalus (SBHC) in British Columbia between 1952 and 1986 inclusive. A total of 479 cases (218 males and 261 females) occurred during this period in 1,298,267 consecutive live births, for an incidence of 3.7/10,000. There were more females, with the sex ratio being significantly different from that of the general population born over this period. No significant seasonal differences were observed over the time period. A comparison of life expectancy for individuals born 1962-1970 and 1970-1986 showed significant improvement in the probability of surviving to the age of 1 year for the latter group. There was also a small but statistically significant increased chance of surviving to age 7 years in the latter group but no difference in the probability of surviving from 7 years to 16 years. Life expectancy figures are shown in a format practical for counseling with regard to prognosis for affected individuals. Additional malformations not attributable to SBHC were observed in 6% (27 cases). These included renal anomalies, cleft lip and/or palate, tracheoesophageal fistula, and diaphragmatic hernia. The incidence of each defect was significantly greater than in the general population of births.