Table 1.

Classical studies of the birth prevalence of congenital disorders

Source	Chromosomal disorders	Congenital malformations	Rare single-gene disorders
Neel (1958)		+
Stevenson (1959)	+	+	+
Stevenson et al. (1966)		+
Trimble and Doughty (1974)	+	+	+
Myrianthopoulos and Chung (1974)		+
Ash et al. (1977)	+	+	+
Hook and Hamerton (1977)	+
Carter (1977)			+
Czeizel and Sankaranarayanan (1984)	+	+

All studies include only disorders that cause death or disability in the absence of intervention