Offspring born out of consanguineous relationships have a higher risk of birth defects according to UK researchers. Their analysis confirms what people have generally suspected to be true.
Children born between relatives, such as blood-related cousins, are at a greater risk of certain genetic disorders and birth defects like Down syndrome, cystic fibrosis, and sickle cell anemia.
Autosomal recessive (autorecessive) disorders occur in individuals who are homozygous for a particular recessive gene mutation. This means that they carry two copies of the same gene (alleles).
As relatives share a proportion of their genes, it is much more likely that related parents will be carriers of an autosomal recessive gene, and therefore their children are at a higher risk of an autosomal recessive disorder.
The extent to which the risk of birth defects increases depends on the degree of genetic relationship between the parents; so the risk is greater in mating relationships where the parents are close relatives, but for relationships between more distant relatives, such as second cousins, the risk is lower – although still greater than the general population.
The low genetic heterozygosity associated with increased consanguinity in a population increases its susceptibility to infectious pathogens such as tuberculosis and hepatitis.
Similar birth defect risks were also slightly higher among women 35 and over, reports MSN Health.
To assess these results, researchers studied more than 11,000 infants born in Bradford, England between 2007 and 2011. Bradford has a large Pakistani community – 37 percent of marriages in were between first cousins, compared with less than one percent of British marriages, reports Health Finder.
The large number of marriages between first cousins accounted for 31 percent of birth defects.
According to lead author, Eamonn Sheridan of the University of Leeds, there is only a small minority of babies born to couples who are blood relatives and older mothers who will develop a birth defect – still the risk is there.
Sheridan’s team noted that marriage between blood relatives is common in many parts of the world. These communities need to be provided with clear information and counseling about the increased risk of birth defects among children born to blood relatives.
The study was published in July’s edition of The Lancet.
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