This isn’t a straightforward yes-or-no
I advise that they wait till the child is born to make a decision. This will help them discern their relationship even better and know if they’re able to be married or not.
If they discover, in the course of the discernment, that they’re not compatible, they can give the baby up for adoption as this is better than either having a teenage mom raise the baby or a couple who don’t like each other marrying and raising a child in a hostile environment. Adoption brings
If they discover they’re compatible with each other and can bear the financial and emotional weight of starting a family, then they can be married when they’re ready.
There’s need to consult with a professional – a priest, a counselor or someone very wise to weigh their options rather than simply take any option that seems okay to them at a particular time. Needless to say, abortion is not one of the options to be discussed.