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Consanguinity |
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What exactly is the information you need to find out? |
If you and your husband/wife are related, it is important that you find out
exactly what the relationship is between you and whether there are any diseases or
developmental problems within the extended family.
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Why is it significant if you are related? |
Family members share a common gene pool. This leads to an increased risk that people who are
related will carry the same defective gene.
If two such people marry (a situation known as a consanguineous marriage) and each transmits the
defective gene to the infant - who thereby receives two copies of the same defective gene - this may
result in the child's suffering from a severe genetic disease.
This type of inheritance is known as autosomal recessive inheritance.
It can occur even if the parents are unaware that they both carry the gene,
since everybody carries 1 - 3 abnormal genes.
However, these are only expressed if his/her partner also carries the same abnormal gene
(out of a total of 70,000 genes). This, of course, is a relatively low risk in the general population,
but in consanguineous marriages, the risk is higher. The risk decreases when the parents are not
first-degree relatives.
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It is important to note that parents who are not related may
also be at risk of having an infant with a hereditary disease of this kind,
but for these marriages (non-consanguineous), the risk is much lower.
Healthy parents who are unrelated have an estimated chance of 2 - 4% of
having a child with a genetic disease, developmental problem or congenital defect.
In contrast, in consanguineous marriages the risk is 5 - 7%, depending on
the degree of the relationship between the parents and their ethnicity.
If in addition to the marriage being consanguineous there is a known genetic
disease in the family, the risk that such a couple will have an infant with a
similar genetic disease may be very high.
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Therefore the risk must be determined during genetic
counseling.
Parents who are related have no increased risk for chromosome disorders in their
fetus. The consideration for performing amniocentesis
is therefore the same as that of a regular pregnancy.
In consanguineous marriages, it is very important to carry out genetic screening
tests for recessive diseases such as thalassemia,
Tay Sachs disease,
cystic fibrosis, etc., and in certain ethnic groups, also for
Canavan disease, Gaucher disease,
etc.
In all cases of consanguineous marriages, genetic counseling should be offered.
This is especially important if, in addition to the partners' consanguinity, there
are known diseases in the extended families or if a problem arises in pregnancy
screening tests.
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