Until they want to hang out with their friends again, without a baby.
Girls become attached to a new born in a way that giving it away can have a far more damaging emotional effect that abortion by far.
That is where the responsibility covertly shifts to the grandmother/grandfather and caring for an infant is exhausting work.
Let me ask you CW, if your son at 15 and his 15 y o GF had a child, kept it and came to live with you, would you be prepared to take on the role as father when "the kids" wanted out after getting over their attachedness
. Maybe you would not object. Doc on this forum seems to take a lot of responsibility for his grandchildren. Ten out of ten to Doc.
Frankly, I couldn't and I would be very disappointed in a daughter who did become pregnant so young.
There is no excuse for it, there are plenty of choices for contraception. I tend to think if it does happen, it is intentional.
If the parent 'gets over the Attachedness', it wasn't real in the first place, much like infatuation rather than real Love. Granted my daughter was a few years older that the hypothetical proposed in the OP, and the father was even older with a previous son. But there has been no reduction in the attachment of either for the children. With the daughter there was no problem hanging out with her friends, many of them were having children of their own, or were really facinated with the young children, so it was like a group of Moms and their kids getting together comparing notes. Likewise the father had taken almost complete responsability for the previous son and I just picked that up when my own grandson came along.
A little aside, my grandaughter has an extremely well developed sense of Humor for her age. Some time ago she was telling my daughters friend, who was taking care of her, that she (the grandaughter) had a wet diaper, or a poopy diaper. Each time when checked, and it wasn't true, and the grandaughter would say "Just Kidding". Just a couple days ago she told me that she pooped her diaper, and it smelled like it (Really "I Farted" in her words). She was completely straight faced as I carried her back to change her, and only when I took the diaper off and found nothing, barely wet, she started laughing and saying "that funny", - 'my reaction' was funny to her.