An inquirer asks about the ruling on proposing to a pregnant woman in her waiting period, and wishes to know when it is legally permissible to marry her.

It is established in Islamic law that it is not permissible for a person to marry the wife of another man, or a woman who is in her waiting period. This is based on the words of the Prophet (peace and blessings be upon him)
who said, “It is unlawful for a man who believes in Allah and the Last Day to water the seed of another”
(recorded by Abu Dawud in his Sunan). This is because such an act would violate the rights of others and lead to lineage confusion.

Regarding the question, it is impermissible in Islamic law to propose to a woman who is in her waiting period (‘iddah) or to become formally engaged to her while she is in her waiting period. The Messenger of Allah (peace and blessings be upon him and his family) forbade a man from proposing to a woman to whom someone else has already proposed. It follows all the more that it is impermissible to propose to a divorced pregnant woman who is still in her waiting period, as is the case in the question.

Once a divorced woman gives birth, her waiting period ends, and it then becomes permissible to propose to her and marry her, as there is no longer any legal impediment.

And Allah Almighty knows best.