Is it obligatory for a Muslim woman married to a non-Muslim man, and who is pregnant by him, to leave him, and how should she act in this situation?

Muslims have unanimously agreed on the impermissibility of a disbeliever marrying a Muslim woman. Her marriage to a non-Muslim is a grave sin, and she must separate from him immediately and repent to Allah. If he embraces Islam thereafter and his Islam is good, there is no impediment to him marrying her anew. As for the fetus resulting from this invalid marriage, it is attributed to its father, because an invalid marriage, if consummated, is akin to a valid one in establishing lineage.