Interrelation of the common congenital malformations: some aetiological implications.

Analysis of congenital defects in a population of 90 921 singleton births revealed a strong interrelation between malformations: for example, 84% of lung defects, 70% of kidney defects, 34% of eye defects, 19% of cleft palate, and 15% of spina bifida coexisted with other defects which could not be designated as subsequently derived structural changes. The strength and intimacy of these interrelations casts doubt on the notion that multiple external factors are involved in the causation of human malformations.