because there were many reports of malformations in babies, people were made aware of the side effects of the drug. the drug causes moderate to severe malformations. most often, limbs are malformed, sometimes they are missing. some side effects affect the formation of bones, the ear, the heart or other internal organs. the most common form of birth defects from thalidomide is shortened limbs, with the arms being more frequently affected. this syndrome is the presence of deformities of the long bones of the limbs resulting in shortening and other abnormalities.