Below, please read a detailed answer from the Islamqa website:
Is it permissible to put the sperm of the husband and the egg of the wife in the uterus of the second wife?
Praise be to Allah.
This method of fertilization, putting the egg with the husband’s sperm in the womb of the other wife is a method that is not permissible according to Islamic teaching, and many scholars are of the view that it is prohibited. Two statements concerning it have been issued by the Islamic Fiqh Council belonging to the Organisation of Islamic Cooperation, and by the Islamic Fiqh Council belonging to the Muslim World League, which originally thought that this method was permissible, then retracted that view. There follows some of what was mentioned in these two statements:
1.. The statement of the Fiqh Council belonging to the Organisation of Islamic Cooperation (formerly the Organisation of the Islamic Conference):
The session of the Islamic Fiqh Council was held 8-13 Safar 1407 AH/11-16 October 1986.
After examining the issue of artificial insemination (test-tube babies), studying the research presented, and listening to the explanations given by experts and doctors, and after discussing the matter, the council determined:
That the methods of artificial insemination that are known at present are seven:
1. Fertilization occurs between sperm taken from the husband and an egg taken from a woman who is not his wife, then the embryo is implanted in the wife’s uterus.
2. Fertilization occurs between the sperm of a man who is not the husband and an egg taken from the wife, then the embryo is implanted in the wife’s uterus.
3. Fertilization occurs between the sperm and egg of the couple, then the embryo is implanted in the uterus of a woman who volunteers to bear it (surrogate pregnancy).
4. Fertilization occurs externally between the sperm of a man and the egg of a woman [not of the married couple] and the embryo is implanted in the wife’s uterus.
5. Fertilization occurs externally between the husband’s sperm and the wife’s egg, then the embryo is implanted in the uterus of the other wife.
6.. Sperm is taken from the husband and an egg is taken from his wife and fertilization occurs externally, then the embryo is implanted in the wife’s uterus.
7.. Sperm is taken from the husband and injected into the right place in his wife’s vagina or uterus, so that fertilization may occur internally.
The council determined:
The first five methods are all haraam according to Islamic teachings and are to be completely banned because of the way in which they are done, or because of what results from the mixing of lineage and the child not being brought up with his real mother, and other matters that are contrary to Islamic teachings.
Regarding the sixth and seventh methods, the council thinks that there is nothing wrong with using them in the case of necessity, whilst affirming that it is essential to take all necessary precautions. End quote.
Majallat al-Majma‘ (3/1/423).
2.. The statement of the Islamic Fiqh Council belonging to the Muslim World League:
Praise be to Allah and blessings and peace be upon our master and Prophet Muhammad (blessings and peace of Allah be upon him) and upon his family and companions. To proceed:
The Islamic Fiqh Council, in its eighth session, held in the headquarters of the Muslim World League in Makkah al-Mukarramah, Saturday 28 Rabee‘ al-Aakhir 1405 – Monday 7 Jumaada al-Oola 1405 AH (19-28 January 1985 CE) examined the concerns expressed by some of its members regarding what the council had permitted in the second clause of the fifth statement having to do with artificial insemination and test-tube babies, which was issued during its seventh session that was held 11-16 Rabee‘ al-Aakhir 1404 AH, the text of which was:
“Regarding the seventh method, in which the sperm and egg are taken from the married couple, and after fertilization in the laboratory, the fertilized egg is implanted in the uterus of the other wife of the same husband, as she volunteers willing to carry that pregnancy for her co-wife, who has had a hysterectomy: it appears to the council that this is permissible in the case of necessity, in accordance with the general conditions that have been mentioned.
Summary of the concerns:
The other wife, in whose uterus the fertilized egg of the first wife is implanted, may become pregnant before her uterus closes following the implantation of the fertilized egg, as a result of her husband having intercourse with her around the time that the fertilized egg is implanted, then she may give birth to twins and not know which came from the fertilized egg and which resulted from intercourse with her husband. As a result, it will be not possible to know who is the mother of which twin. Moreover, one of the two embryos may die in the early stages of pregnancy, and not be expelled except with the birth of the other, and it will not be known whether the surviving child grew from the fertilized egg or from the pregnancy that resulted from the husband having intercourse with her. This would result in the mixing of lineages and it would not be known who the true mother is of either child, and this would affect rulings that are connected to that. All of this dictates that the council should retract its ruling regarding the case mentioned.
The council also listened to opinions presented by gynecologists and obstetricians who attended the session and confirmed the possibility that a pregnancy could result from intercourse with the husband at the same time as the pregnancy resulting from the implanting of the fertilized egg, and that could lead to mixing of lineages in the manner mentioned in the concerns referred to.
After discussing the topic and exchanging views on it, the council decided to retract its view regarding the permissibility of the seventh method referred to in the statement previously issued by the Council in its seventh session held in 1404 AH. End quote.
Qaraaraat al-Majma‘ al-Fiqhi (p. 159-161).
Based on that:
It is not permissible to take the sperm of the husband and the egg of the wife and put this mixture in the uterus of the husband’s other wife.