Another way that the health problems can start is because teens might not have all the knowledge of proper behavior in knowing how to nurse the child or the proper ways during the growth of the child.
Teenage adolescents tend to develop poor eating habits during pregnancy, they tend not to take the proper vitamins, and in the worst scenario the teen drinking and/ to doing drugs during the pregnancy.
That is the worst that can be done; it will increase the chance greatly of the baby being born with some type of birth defect or a weak part of the baby.
Now that can be the worst you can possibly do to an unborn child.