If he killed the pregnant woman, yes. If he caused a miscarriage, that is still a violent crime and a horrible thing but not manslaughter.
Besides, as mentioned in the OP:
The Medical Examiner detected a congenital abnormality, placental abruption and chorioamnionitis as well.
Babies are born with medical problems due to drug/alcohol use in utero, but they are born alive. This fetus clearly had a number of medical reasons why the pregnancy was not going to make it all the way.
