The so-called "crack baby epidemic" was an invention of drug war propagandists to justify the war against drugs. While it may be safely assumed that cocaine is not good for pregnant women or their babies, there is no evidence that the crack use alone caused any lasting harm to these children.
As one example, ABC did a feature on the crack babies on one of their shows about popular myths. They found that most of the children who had been labeled as "crack babies" had suffered more from the stigma of being labeled as a damaged child than they had suffered from the crack. One of the "crack babies" they featured turned out to be a concert pianist before she was in her teens -- quite a talented and bright person.
See The Myth of the Crack Babies at http://www.druglibrary.org/schaffer/cocaine/crackbb2.htm