What's so bad about teenage parenthood?

In the parts of the world where a teen is working, earning a living and taking on mature roles at an early age this isn't necessarily a bad thing because they also get married young and have usually grown up in large, close families so they're not completely inexperienced with babies and they have plenty of help. The developed world model of this though rarely includes a committed partner, too often involves still being financially dependent on parents and generally unfairly burdens the rest of society because the teen has punted on education and will be on public assistance for years if not forever. This is one of the primary drivers of childhood poverty in the US. 

nothing as long as youre mature for it

Who is able to support a family as a teen? Housing, food, clothing, medical expenses etc.

nothing if youre mature enough to have a child