Healthy people make a healthy community. Modern medical breakthroughs and the possibility to discover potential diseases have encouraged people to be more willing to take precautionary measures to avoid future sufferings. As a consequence, this has given rise to the issue of undergoing medical examinations before getting married to spare the man and the woman as well as their prospective children unnecessary health problems.
Dr. Rajab AbuMleeh, Ph.D. in  Shari`ah, stated:

Pre-marriage (mutual) medical check-up is among the matters that have been introduced into Islamic fiqh and in turn the path for issuing fatwas on it is still unpaved. This is because there are no established statements from earlier jurists on this issue. Hence, judging it will be based on the fiqh of Muwazanat (balancing benefits and harms) regarding the benefits and harms of having such a checkup, and giving preponderance to that which outbalances the other.

In spite of the benefits expected as a result of having these check-ups – such as in the case when a person has a chronic disease or when one of the prospective marriage partners should be advised to refuse the marriage (proposal) – still we cannot overlook the involved harm. These check-ups may disturb some people’s lives. When the results of such check-ups are negative, this will affect the relation of sick people to those who are healthy and all this will be made known.

Thus, as contemporary scholars have examined the benefits and harm, they came to the conclusion that it is permissible to have such check-ups, without them being made mandatory by the state or by society. They added that it is the right of the prospective bride and groom, meaning that they could either demand or disregard it.

Furthermore, the Islamic Fiqh Academyof the Muslim World League has reviewed the issue of medical check-ups, which means having a medical check-up using all available methods (including radiography, medical analysis, and genetic examination), in order to know whether either the bride or the groom has an infectious disease or a disease that could affect the objectives of marriage. Following deliberation and discussion of the researches conducted on the issue, the council has decided the following:

First: Indeed, a pre-marriage medical check-up has benefits as regards the detection of infectious or influential diseases that may determine or undermine the prospective marriage. However, it – especially genetic examination – has disadvantages and risks as regards divulging hidden things, and the harm it entails to the sick person (physiological harm) and to his future.

Second: Legally, there is nothing that precludes having a medical check-up, including genetic examination, since it could be of benefit in treating diseases, but with the condition of observing secrecy.

Third: There is nothing that prevents either the bride or the groom from stipulating that the other partner run genetic tests before marriage.

Fourth: There is nothing that precludes their agreement to having a (non-genetic) medical check-up before marriage on the condition that they both (bride and groom) adhere to the Islamic ethics of keeping secrets and avoiding harming each other.

Fifth: It is not permissible for either of them, upon marriage, to hide any infectious or influential disease he or she may be suffering from – in case there is any – from the prospective marriage partner, and in case one does so, and in turn the other is infected with the disease or dies as a result of it, then the partner causing it bears all consequent penalties and indemnities according to the rulings and the regulations of the Shari`ah.

Sixth: Both of them have the right to demand revocation of the marriage, after contracting it, in case it is proven that the partner is suffering from an infectious disease or a disease that affects the objectives of marriage.

Dr. Muhammad `Ali Al-Baar says: There is nothing that prevents having a medical check-up for those intending to get married that proves they are free from infectious diseases, manifest genetic defects or genetic defects existent in the health history of the family. Moreover, they – at least – should be sure that neither partner has sexually transmitted diseases – either through adultery or sodomy – and that, in case one is suffering from a disease, it is treated before contracting the marriage. There is a new branch in medicine that is called genetic counselling, which first emerged in Western countries.

Furthermore, Dr. Hussam `Affanah, Professor of Fiqh and its Fundamentals in Al-Quds University, Palestine, says,

Having a pre-marriage medical check-up is legitimate, and its legitimacy is proven by general proofs that prescribe seeking medication. It is also known that a pre-marriage medical check-up is a means of prevention, knowing that prevention is better than cure.
Moreover, it is well-known that among the objectives of marriage in Islamic Shari`ah is to beget children and that such children should be healthy, both physically and morally. Moreover, the children cannot be healthy unless they are free from diseases, especially genetic diseases. Almighty Allah says through the tongue of Zakariyah(Zachariah), peace be upon him, (O my Lord! Grant me from You, a good offspring. You are indeed the All-Hearer of invocation.) (Aal `Imran 3: 38) Besides, the believers invoke their Lord saying, (Our Lord! Bestow on us from our wives and our offspring who will be the comfort of our eyes, and make us leaders for the Muttaqun (pious).) (Al-Furqan 25: 74) Indeed, offspring cannot be the comfort of the eyes when they are deformed, mentally retarded or disabled.
In addition, the Prophet (peace and blessings be upon him) urged those who intend to get married to choose their wives well, as it was stated in the hadith reported by`A’ishah(may Allah be pleased with her) from the Prophet (peace and blessings be upon him) that he said, “Select (good wives) for your sperm, and marry the competent (husbands) and get (your progeny) married to them“. [IbnMajah, and Sheikh al-Albani said in SahihSunanIbnMajah that it is a sound hadith (1/333)]
It is also reported from AnasibnMalik that the Prophet (peace and blessings be upon him) said, “Marry the affectionate and the fertile.” (Ahmad and declared authentic by IbnHibban and al-Hakim.)
Moreover, `Umaribn al-Khattab (may Allah be pleased with him) was asked, “What is the right of the child over his father?” He replied, “It is that he selects his mother well, gives him a proper name and teaches him the Qur’an”.
Selecting a wife properly means considering physical and spiritual traits. This is in line with the Prophet’s (peace and blessings be upon him) saying, “A woman may be married for four things: her wealth, her lineage, her beauty and her religion (religious commitment). So, seek the one who is religiously-committed, may your hands be rubbed with dust (i.e., may you not prosper; if you do not do so).”  [Al-Bukhari and Muslim]