The answer to this is neither yes or no.
While it's far from the most ideal situation (in our culture) for a 16 year old to become pregnant, it does happen. Most often the parents were not intending on having a child.
The important thing, in this situation, is that the parents deal with what's happening in a mature manner, consider their options seriously, make a decision (preferably together) on what to do.
As long as the parent(s) can handle it, physically, emotionally, financially and have a good support system around them I don't see a problem with someone young raising a child.
I think it's important for parents to start talking realistically about intercourse and pregnancy and babies to their children as soon as the children begin to ask questions. I've seen a few teenage mums who said they seriously didn't even know that they could get pregnant or how to use what protection they had.
I'm sarcastic a lot. If I offended you I probably didn't mean to. Probably.