Incidence of congenital malformations in Tokyo Metropolitan Hospitals, 1979–1993

Congenital malformations in all babies delivered at 11 Tokyo Metropolitan Hospitals (TMH) (8 hospitals since July 1989) for 15 years, January 1979 to December 1993, were monitored. Congenital malformations found within 7 days after birth were observed in 2085 babies (1.5%) of 138 544 births including stillbirths after 16 weeks gestation. The prevalence rates of selected malformations were calculated and compared in the 5-year periods of 1979–1983, 1984–1988 and 1989–1993. There was no typical secular trend in prevalence rates of malformations except for the heart and circulatory system, which showed an increase because of the recent progress in prenatal diagnosis of these malformations. The specificity of the TMH Monitoring System is also discussed.