Is the wife sinful for leaving the home and refusing to return if the husband does not acknowledge the invalidity of the marriage that took place after adultery and before repentance from pregnancy, or is she sinful for staying with him?

The issue of a fornicator marrying a fornicatress before repentance and ensuring the womb is clear is a matter of scholarly disagreement. This website has adopted the madhhab (definition) (school of thought) of Imam Ahmad, which stipulates repentance and ensuring the womb is clear. However, some jurists validate the marriage contract before repentance or even if there is a pregnancy, provided it is from him. Since the questioner has embraced Islam, her repentance is confirmed. The Hanafis and Shafi'is permit marrying a pregnant woman conceived through zina (fornication/adultery) and having marital relations with her after the contract, if the zina was committed by him. It is more prudent to renew the marriage contract to avoid disagreement. However, if her husband has sought a fatwa (definition) from someone who validates the marriage, or if he has followed the Hanafi or Shafi'i schools, then he is not obliged to renew the contract, and she does not sin by remaining with him. The renewal of the contract takes place between the husband and the Muslim wali (guardian), with two witnesses. If there is no Muslim wali, the Imam of the Islamic Center may act as her wali for the marriage.