The study of birth defects has assumed an importance even greater now
than in the past because mortality rates attributed to congenital
anomalies have declined far less than those for other causes of death,
such as infectious and nutritional diseases. It is estimated that as
many as 50% of all pregnancies terminate as miscarriages. In the
majority of cases this is the result of faulty development. Major
congenital malformations are found in at least 2% of all liveborn
infants, and 22% of all stillbirths and infant deaths are associated
with severe congenital anomalies. Teratological studies of an
experimental nature are neither ethical nor justifiable in humans.
Numerous investigations have been carried out in laboratory animals and
other experimental models in order to improve our understanding of
abnormal intra-uterine development. In less than two decades the field
of experimental teratology has advanced phenomenally. As a result of the
wide range of information that is now accumulating, it has become
possible to obtain an insight into the causes, mechanisms and prevention
of birth defects. However, considerable work will be needed before these
problems can be resolved. This book brings together some of the more
recent and important research findings related to the mechanisms and
pathogenesis of abnormal develop- ment. It is not only a documentation
of the latest experimental work, but it also points out future
directions that seem productive and challenging.