The Dutch National Institute for Public Health and the Environment (RIVM) says that almost 25% of Turkish and 20% of Moroccan parents in Rotterdam are married to a family member. Children of related parents have a higher chance of birth defects. Information and a genetic examination are necessary in order to bring down the number of disorders.
The study was conducted on request of the ministry of health, due to the higher death percentages among immigrant children.
Marriages between cousins, second cousins and uncles and niece bring about an even higher risk of rare genetic disorders. There are thousands of such disorders, from mental retardation to hereditary anemia. Some are fatal.
Studying the consequences of blood-relationships is hard: there is no national data about all birth defects and the number of marriages between family members is not registered.
For an indication of the number of blood-relationship marriages, the RIVM asked for data from the Rotterdam Generation-R study. The study followed up on 10,000 newborns. Of the 653 Turkish parents who took part in the study, 24% were married with family. Of the 474 Moroccan parents, 22% were married with family.
The study about the effect of these Rotterdam marriages on the children's health is not yet finish. but from a study of children in Groningen, Friesland and Drenthe it appears that immigrant parents of children with birth defects are related six times more often than ethnic Dutch parents.
The RIVM thinks that family marriage should be considered a risk factor for birth defects, just as motherhood at a later age. Screening and prenatal examinations are therefore needed.
Screening programs for blood-related parents have been set up abroad and have brought down the number of birth defects.
According to the RIVM, the higher mortality rates among immigrants cannot be explained only by the parents' blood relationship. Causes such as bad social-economic situation also play a role.
Source: Volkskrant (Dutch)
See also: UK: Minister warns of birth defects among immigrants, Netherlands: Proposal to ban cousin marriages