Ruling on marriage for one who is a carrier of sickle cell anaemia
Question

What is the Islamic ruling on marriage for a man or woman who is a carrier of the sickle cell anaemia gene?
Praise be to Allah.Firstly:
Sickle cell anaemia is a type of inherited anaemia that results from changes in the shape of the red blood cells, which become crescent -shaped (like a sickle, from which the name of the disorder is derived) when there is a lack of oxygen.
Symptoms include:
1. Short-lived red blood cells, which leads to chronic anaemia. A lack of growth and inability to engage in activities may be noted.
2. Severe pain in the joints and bones. Blockage of the capillaries feeding the brain and lungs may occur.
3. Continuous erosion in the bones, especially the pelvic bone and the knees. There may also be an enlargement of the spleen, which may lose its function.
4. This disease is accompanied by sudden crises that cause a sudden breakage of blood cells. That is often the result of some infections and is indicated by the yellowing of the eyes to a noticeable degree and a severe drop in haemoglobin that requires a blood transfusion.
One who carries this gene, who does not display any symptoms – and also one who is affected by this sickness – may marry someone who is healthy and produce healthy children. But it is risky for him to marry someone who is affected by this disease or is a carrier of the gene like him, because his children may be vulnerable to this disease.
Secondly:
Undoubtedly one of the objectives of marriage is to produce righteous offspring and increase the numbers of the ummah of Muhammad (blessings and peace of Allah be upon him), as is mentioned in the hadith which was narrated by Abu Dawood (2050) from Ma‘qil ibn Yasaar (may Allah be pleased with him), who said:
A man came to the Prophet (blessings and peace of Allah be upon him) and said: I have found a woman who is of good lineage and beautiful, but she cannot have children; should I marry her? He said: “No.” He came to him a second time, and he again told him not to marry her. Then he came to him a third time, and he [the Prophet (blessings and peace of Allah be upon him)] said: “Marry those who are loving and fertile, for I will be proud of your great numbers before the other nations.” This hadith is classed as saheeh by al-Albaani in Irwa’ al-Ghaleel, no. 1784.
One of the requirements of that is that the children who are produced should be healthy and able to carry out their duties.
If the prospective spouses know that getting married could lead to producing children who will develop this sickness or who will be carriers of this gene, then what is best is for them to refrain from getting married in that case, so as to ward off this expected negative outcome, and so as to reduce evil and harm in the Muslim ummah, and to protect themselves from the hardship and anguish that they will face whilst caring for the sick child.
In terms of permissibility, it is permissible for a carrier of this gene or one who is affected by it to marry someone who is healthy or is affected by the disease, if she accepts that, after informing her of his condition, and they may agree not to have children.
It is not permissible for either of them to get married without disclosing his sickness, because concealing that is a kind of deceit and is forbidden.
And Allah knows best.