According to the March of Dimes, women under the age of twenty have greater chances of premature babies, babies with low birth weight, other serious health problems and death. But, from what I understand, this has more to do with the behavior of teens than their physical age. Teens are more likely to smoke during pregnancy, less like to receive adequate prenatal care...
The psychological effects, however, are harder to prevent. Teen mothers have less chance of completing high school or receiving higher educations so their earning power is limited; many teens wind up on some type of assistance to make ends meet. Teen mothers are less likely to have men in their lives that are responsible fathers. Children of teen mothers are moe likely to be teen mothers themselves- more likely to do a whole host of things that are bad for them.
I don't so much believe it is wrong or right for a teen to have a baby. I think ANYONE that has a child should give them the best life possible. (I know a woman who was married and emancipated at the age of seventeen. She finished high school, got a full time job that paid reasonably well, got married and had a baby all before she turned twenty. She and her husband made a conscious decision to have a child and they had a complete nursery, health insurance and savings to give the baby a good start.) I'm not recommending that other teens do this- she wound up divorced before she was twenty- five- but the point is she did everything she could to give her son the best start possible. Unlike my friend, I think most teen mothers who deliberately get pregnant are thinking more of themselves than they are of their children. If they did, they would wait until they were in a more stable position- finished with school, more able to support a child, in a legally committed relationship with the child's father, able and willing to get the proper prenatal care...