Limb malformations are relatively common,the incidence being 0.6/1000 live births. Some of the congenital abnormalities of the limbs could be assigned to a specific genetic or teratogenic cause. However, most of the limb malformations appear to have a multifactorial etiology, arising form an interaction between environmental influences and the genetic make up of the developing individual.
A variety of drugs have been found to cause limb defects. Thalidomide is the most notorious teratogenic drug. Mothers who used this drug during early pregnancy gave birth to babies with severe limb defects. There is strong suspicion that some other drugs like aspirin, dimethadione (an anticonvulsant drug) and vitamin A (retinoic acid) may have teratogenic effects on the development of limbs. Clinical studies show that the most critical period for teratogen induced limb anomalies is the 4th and 5th weeks of intrauterine life. Oligohy-dramnios and amniotic bands can also cause various limb deformities. Congenital limb malformations are also associated with other conditions which cause constriction of the space within the uterus, e.g. bicornuate uterus (a congenital anomaly of uterus), and large fibroids (a variety of benign tumors of myometrium).