Nej, something very similar happened to my younger brother, though he broke up with his girlfriend because she had cheated on him several times. In her attempt to get him back, he made a dumb ass move and slept with her one more time.
Boom, pregnant, despite successfully using birth control throughout their four-year relationship. He was definitely at fault too, for not using a condom.
Neither believed in abortion, and she still wanted him back so they could be a "family." He planned to support her and the baby... but he made it clear that he didn't want to be with her because he couldn't trust her to be faithful.
She flipped the hell out and has been making his life miserable ever since, going on six years now. Every time he gets visitation, it's taken away a few months later or she just refuses to let him see his daughter. The family court continually favors her, despite marrying a known drug user, using drugs herself and serving six months in jail for shoplifting (her mother was granted temporary custody over my brother, for some ridiculous reason). She even got married, had another baby and divorced the guy, but her ire remains focused on my brother.
I would say, especially if your friend and his girlfriend haven't been dating long, a paternity test is necessary in case she tries to rake him over the coals legally. If/When it's established that the child is his, he needs to step up and take responsibility. He effed up, too. If he wants joint custody or visitation, he needs a good lawyer. My brother's endless line of county-appointed attorneys have been utterly useless. And, uh, use condoms in the future, even if his partner says she's taking the pill.
But I hope he's able to work with her on having a civil relationship for the baby's sake. It doesn't deserve to be the pawn of a resentful parent.