ABSTRACT
For this new version of the book, we also decided to add this chapter on malformations in twins and multiple pregnancies. However, because this text is malformation oriented, we have concentrated on congenital anomalies, leaving out most of the important issues related to the genetics of twinning and risk of preterm delivery. Hence, in this chapter, we will deal with the following questions: (1) when is the risk of finding a congenital anomaly increased in twins; (2) what type(s) of anomalies are more likely to be present; and (3) is there any anomaly specifically related to the developmental pathology of twinning?
