Consanguineous marriage is referred to a marital union between a male and female with the blood bond. Considering the degree of closeness, the most disadvantageous consanguineous marriages occur between two first-degree cousins; who are the children of aunts and uncles. Marriages between grandchildren of siblings and marriages between second-degree cousins pose a lower risk of genetic disease transmission compared to marriages between two first-degree cousins.
Hereditary diseases that occur as a result of consanguineous marriages are usually metabolic diseases; which are quite numerous. Screening all types of metabolic diseases is not possible in any country around the globe today. However; if a hereditary disease in the family is known or if the couple has already a child with such a disease, these diseases are screened in the embryos obtained by in vitro fertilization. After such screening, only healthy embryos are transferred.