I feel like age isn't quite as important to child-rearing as is one's financial stability and personal maturity, which are both very important factors in raising children, in my humble opinion.
It's not that I have children, or want to soon, but when I do, I want to be well-prepared, both mentally and financially.
Alas, we do not live in a perfect world - even with contraception and birth control, accidental pregnancies still occur. The odds are astronomically low, but there is still a chance, and it has happened before.
So, in the case that one is exposed to such a situation, I believe that they have quite a few options, and should make the one that best suits what they believe and also their personal situations.
For example, if they feel like they are not fit mentally to be parents, they could allow someone to adopt their child, and although I discourage it, since the foster care system is relatively writhe with abuse, I personally prefer it to abortion. Although, there is the possibility that some would prefer abortion to giving their newly-born children to a perfect stranger.
In any case, regardless of how well or ill-prepared one is, I still believe that decisions should be made carefully, instead of jumping headlong into a difficult situation without much though.
That is all I can really offer on this matter for now.