Incidence of neural tube defects in liveborn and stillborn infants in British Columbia over a 10-year period.

Reports of an apparent decline in the incidence of neural tube defects (NTDs) have come from various parts of the world. If these findings are consistent they would have an important impact on prenatal diagnosis and on screening programs. The incidence of NTDs over a 10-year period was examined in British Columbia, a province that has a population-based health surveillance registry through which there is virtually complete ascertainment of liveborn infants with NTDs. The results showed a significant decrease in incidence only for stillborn infants with anencephaly. The increased use of ultrasonography and the subsequent termination of pregnancies in which the fetus has been found to have anencephaly may explain this observation.