If it's a girl, either she married the man she slept with or she gets punished for being a skunk. Ideally, have her get married before she has the chance to do it.

If it's a boy, well, depends. I would say he is better off focusing on his studies, work, etc, but if there's no way around it, he would have to marry the girl and start working earlier to sustain her. Otherwise, as long as he can avoid getting the girl pregnant, then it's fine.... for him. The girl will lose part of her value, obviously.