What are the opinions of scholars regarding the necessity of the 'iddah (waiting period) for a woman in the event of an invalid contract and the husband's desire to renew it with a valid contract, and does the fatwa differ if the woman is pregnant or if the matter pertains to fornication?

The waiting period (iddah) becomes obligatory upon sexual intercourse in a void marriage (nikah fasid) by scholarly consensus. The iddah is also established by mere privacy (khalwa) according to the Hanbalis in a marriage whose invalidity is disputed.

If the former husband wishes to renew the marriage contract with her during her iddah from his void marriage, he is permitted to do so according to most scholars.

If the woman is pregnant from a void marriage, the man from whom she conceived is permitted to marry her before she gives birth, because the iddah is to preserve his lineage.

As for a woman pregnant from zina (fornication/adultery), her iddah is the delivery of her child. It is permissible, according to the Shafi'is and Hanafis, for her to marry before giving birth, because the lineage from zina has no sanctity.

If someone other than the fornicator marries her, it is not permissible for him to have intercourse with her until she gives birth.