Marriage between relatives is a marriage realized between people who are having a blood-relation. The first level of marriages between relatives is the ones among cousins, the children of uncles or aunts. The rate of that in Turkey is 21% and it is the highest rate in the world excluding e few isolated society.

In general 2% of every 100 children have some anomalies. The risk is doubled (4%-5%) in marriages among in the families.  Therefore these pregnancies have to be checked regularly and second level ultrasonography must be conducted. Some scanning tests for the diseases such as phenylketonuria and recessive diseases seen mostly newly born children must be realized. Besides these couples because of the fact that symptoms are occurring in the stage of growths, after the birth, should be warned about recessive genetic disease for their successive pregnancies and they have to be told that they have to wait for the second pregnancy at least 1-2 years.

That marriages between relatives increases to carry the same mutant gene is increases the risk of occurring of autosomal recessive diseases. After having encountered the disease in a pregnancy, the risk is %25 for every successive pregnancies.