What is the ruling on a man marrying a woman whose husband divorced her while she was pregnant in the early months, and then the other man married her before she gave birth? Is the first marriage contract considered legally valid, or must the other man remarry her?

The 'iddah (waiting period) of a pregnant divorcee ends with childbirth, by consensus, and it is forbidden to marry her before then, based on the Almighty’s saying: (And for those who are pregnant, their term is until they deliver their burdens), and the Prophet's saying, peace and blessings be upon him: "It is not permissible for a man who believes in Allah and the Last Day to irrigate with his water the crop of another." Marrying a woman undergoing her 'iddah is invalid and forbidden by consensus. One of the conditions for a valid marriage is that the woman be free of impediments, such as the 'iddah. If a man marries a woman during her 'iddah, and both are aware of the ruling, their act is considered zina (fornication/adultery), and they are subject to the prescribed punishment, and lineage is not established. However, if they were ignorant, then lineage is established, the punishment is waived, and the dowry is due. If one was aware and the other ignorant, then each case has its specific ruling regarding the establishment of lineage, dowry, and punishment.