NEURAL-TUBE DEFECTS 1974-94 - DOWN BUT NOT OUT

Aims-To describe accurately the total prevalence of neural tube defect s (NTDs) in England and Wales over time, and to provide a benchmark up to 1994. Methods-National data about NTDs reported as births or termi nations are available from 1974-94, but reporting is incomplete. A loc al register of NTDs covering Oxfordshire/west Berkshire from 1965-94 w as used to validate national data for the locality, using the method o f capture and recapture, and hence to estimate incompleteness of repor ting nationally. Results-National underreporting is consistent at abou t two thirds of the true number of cases reaching at least the second trimester. The local register is much more complete, but time trends l ocally and nationally are similar. In England and Wales total prevalen ce declined from about 34 per 10000 live and stillbirths in 1974 to a plateau of just under 8 per 10000 in the 1990s. Conclusions-The declin e in NTD prevalence is real and seems to have stopped. How this relate s to changes in diet or the practice of vitamin supplementation is unk nown, and the implications of the plateau are uncertain. OPCS figures of 500 NTDs annually in England and Wales represent about two thirds o f the true number of cases.