SINCE 1941 I have begun the section on congenital deformities with an article by Josef Warkany. I will follow the now established custom and do the same this year.
He says320 that congenital defects are deviations from the normal which are present at birth. Such defects may be morphologic or functional and may be hereditary or acquired, but they are always determined before birth. The fact that mammalian congenital defects arise in the maternal uterus, seemingly uninfluenced by visible environmental factors, has kept their origin obscure and their prevention beyond human influence. Superstition and confusion have been and still are prevalent in the speculations on the origin of congenital defects, more so than in any other field of human pathology.
We must look to embryologic morphology and embryologic chemistry for an understanding of prenatal development. A continuous chain of physicochemical reactions regulates the development of the unborn child from