Is it obligatory to inform the husband of one's inability to conceive, after his sick wife, who was seeing a doctor for treatment, became pregnant?

What is understood from the question is the belief that the woman became pregnant from adultery, and that her husband is not the father of the pregnancy. This is serious, and if the questioner articulates it, it would be an accusation of unchastity against the woman. Allah has warned those who accuse chaste women, stating: "And those who accuse chaste women and then do not produce four witnesses - flog them with eighty lashes and never accept their testimony thereafter. And those are the defiantly disobedient." And: "Indeed, those who accuse chaste women, unsuspecting [of evil], believing, are cursed in this world and the Hereafter, and for them is a great punishment." The Prophet, peace and blessings be upon him, counted accusing chaste women as one of the seven destructive sins. Therefore, it is not permissible for the questioner to inform the husband of what was mentioned, because it is an accusation of unchastity against the woman, and it will lead to corruption between the spouses, and because it is an unverified matter, as the results of tests are often presumptive and not definitive.