Consideration on the methodology of a simple and effective birth defect monitoring system

In detecting changes of the occurrence of birth malformation it is important to indicate the prevalence of environmental hazards. The Tottori Monitoring System for Birth Defects (TOM) is a small regional system covering 6,000 births yearly which was started in 1974. The system is made up mainly of two projects: a monitoring system for reporting congenital malformation and an epidemiological and genetic study for neuro-developmental and genetic disorders. The former system has changed its sampling procedure four times during the past 26 years because of the difficulty in getting cooperation from local administrations and from all maternity clinics in the Tottori prefecture. We have compared those four changes in the system with the following criteria: availability, reliability, durability, operationality and confidentiality. Our conclusion is that the population-based system which received positive support from the administration and almost all obstetricians in the field was the best in quality. On the other hand, the hospital-based system organized by a small group of pediatricians and obstetricians who belong to core hospitals in the field was a simpler but useful system for maintaining durability, operationality and confidentiality. It is, however, important to note that the data collected by the hospital-based system showed a relatively lower frequency in serious malformations like anencephaly and non-emergency malformations like syndactylia as compared with those collected by the population-based system. If an inter-regional collaboration among the similar local systems in Japan could be set-up, a useful network could be developed eventually acting as an ideal population-based system.