There is nothing wrong, as far as Islam is concerned, in giving zakah to help a sterile woman have an in vitro fertilization operation if that woman can’t afford paying the costs of the medical treatment.
Dr. `Abdullah Al-Faqih, supervisor of the Islamic Web, states the following: If the woman in question is principally a worthy recipient of zakah (being poor, for example,) there is nothing wrong about paying the zakah to her. Allah Almighty says: (< font>The alms are only for the poor and the needy, and those who collect them, and those whose hearts are to be reconciled, and to free the captives and the debtors, and for the cause of Allah, and (for) the wayfarer; a duty imposed by Allah. Allah is Knower, Wise.) (At-Tawbah 9: 60)

But it is to be taken into consideration that (human) artificial fertilization is not lawful in all cases in the point of view of Islam. It is allowed only when there is no alternative way for the couple to impregnate the wife. Also, it is to be done under certain conditions, such as that the embryo to be deposited in the woman’s uterus be the result of the fertilization between this same woman’s ovum and the sperm of her husband.
If these conditions are met in the case of the woman the questioner wants to pay zakah to, it is lawful for him to pay zakah to her. But if there is something unlawful concerning the fertilization procedure [such as when the ovum is not hers, or the sperm is not her husband’s], we advise the questioner not to pay zakah to her in this case so that he does not participate in an act of disobedience to Almighty Allah. He Almighty says: (Help not one another unto sin and transgression, but keep your duty to Allah. Lo! Allah is severe in punishment.) (Al-Ma’idah 5: 2)