Saudi Arabian Pre-Marital Tests

I'd never heard of this until reading this, but it is fascinating:

Pre-marriage tests focus on hereditary blood diseases (sickle cell anemia and thalassemia) and some contagious diseases like hepatitis B and C and AIDS due to fear the other party might contract the disease or the children might be afflicted in future. Choices and alternatives are placed before the prospective couple to help them plan for a sound and healthy family and disseminate awareness according to the concept of a comprehensively healthy family.

Among the diseases that cause concern for engaged couples is sickle cell anemia, which is considered a common factor for all these tests and diseases, as it is the most common disease in some regions of the Kingdom and in many other Gulf countries...

Khaled Imad said the stories on pre-marriage tests have dashed the dreams of many people wanting to get married. A large number of them have fears about undergoing the premarital tests. He said he asked a young woman’s hand in marriage two years ago. When they conducted the tests the results did not match. He was forced to repeat the tests several times and is still doing them.

Maha Abdulkhaliq said the center discovered her test results and those of her fiancé did not match. They accepted the matter calmly and are now undergoing special treatment for hereditary diseases. They delayed their marriage for a year to undergo treatment.

As indicated by the last paragraph, these  tests do not create a binding legal prohibition on marriage, and are instead meant as a preventative family health measure.  I suspect that part of the reason for this system in Saudi Arabia lies in the traditional Arabian practice of parallel cousin marriage.  That's a great way to keep property in a family, but in the long run introduced many problems because of the restricted gene pool.