Child support is a serious matter, and failing to provide support for your child can have very serious consequences. Your assets (savings accounts, tax returns, even lottery winnings) can be frozen and used to pay the child support debt you owe to the Office of Child Support Enforcement. Your driver's license can be suspended, and you will receive a negative mark on your credit rating, making it hard to get loans, credit cards, or even rent an apartment. If you fail to attend a court hearing on your non-payment of child support, you can even go to jail. Even if you're under 18, you'll still be expected to pay child support.
The bottom line is this: raising a child requires a lot of work, money, and responsibility from both parents; and all of these things are difficult to manage when you're still a teenager. It's much better to wait until you're an emotionally mature and financially stable adult.