Many theories have been suggested to explain the causation of congenital malformations. A number of observations1 have been made to support the contention that the environment of the ovum after fertilization can be influenced sufficiently to modify its growth and development. It is, nevertheless, generally accepted that most congenital malformations are due to intrinsic or inherited factors. The evidence that
defective germ plasm prior to fertilization of the ovum is responsible for congenital malformations was reviewed by Murphy.2 He could find no evidence to suggest that malformations result from environmental factors which operate for the first time after fertilization has taken place.
Recently, however, it has been suggested that there is a relationship between certain acute infectious diseases suffered by the mother early in her pregnancy and the development of anomalies in the offspring. Gregg,3 in 1941, was the first to suggest this, in his report of