Can a husband obtain a fatwa stating that the child is illegitimate (ibn haram) with the aim of nullifying the rights of the wife and the newborn, despite his knowledge that the child is his and that the marriage took place during the pregnancy?

If a man commits adultery with a woman and she becomes pregnant by him, he should not marry her until she gives birth. Some jurists permit contracting the marriage while she is pregnant, provided there is no intercourse until she gives birth. Others permit both the contract and intercourse. If the marriage takes place and she gives birth after six months or more from the contract, the child is attributed to him, and he cannot deny paternity except through li'an (oath of mutual imprecation). If she gives birth to a live baby in less than six months, the child is not his, and he has the right to deny paternity.

Some of the Salaf (early Muslims), and Ibn Taymiyyah chose this opinion, permitted the father to attribute the child to himself. The Hanafis said: He has the right to claim the child and attribute it to himself, provided he does not say that it is from zina (fornication/adultery). If six months or more have passed between the marriage contract and the birth of the child, the husband cannot deny the child except through li'an, and li'an is permissible only for denying paternity.

If the husband denies the child, whether through li'an or otherwise, the child has no right to maintenance or inheritance from him. As for the wife, if she has a deferred mahr (dowry), it is not forfeited by the denial of the child.