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Genetic Examination of Recurrent Miscarriages

Genetic Examination of Recurrent Miscarriages

Recurrent miscarriages are mostly observed during the first trimester of pregnancy. They are a relatively common reproductive problem and usually affect 10-15% of the total number of pregnancies worldwide. When miscarriages are repetitive and can no longer be considered a random fact, investigating the cause is important for the couple to make the right decisions. The examination is particularly valuable for the detection of any chromosomal abnormalities that cause about 60% of the first trimester abortions and 20% of the second trimester abortions.

95% of the chromosomal abnormalities detected in abortus tissue samples are numerical abnormalities (less or more chromosomes than the normal number). These abnormalities are not detected in the karyotype of the parents – which is normal – and are considered to appear for the first time in the family (de novo).

The rest 5% of the detected chromosomal abnormalities is associated with structural chromosomal abnormalities of the fetus, usually inherited by a healthy parent, who is however a carrier of the chromosomal abnormality.
If the karyotype of the abortus reveals a chromosomal abnormality, then it is considered that the cause miscarriage has been determined. In this case, no further tests are considered necessary for the couple, except from tests of a genetic base.

It should be noted that chromosome abnormalities that can be identified with conventional karyotyping are numerical abnormalities and structural abnormalities exceeding a certain size limit (> 10MB). The conventional karyotype analysis has internationally a success rate of 60-90%, because in some cases it can not be performed successfully due to the necrosis of the tissue or because of other problems related to the technique itself.

Molecular Karyotype
Molecular Karyotype may replace the use of conventional karyotype when examining abortion material. When abortus tissue cannot be cultivated due to decomposition, then molecular karyotyping can be an alternative test for the diagnosis of some chromosomal abnormalities cases.

In particular, special tests are performed that can detect the most common aneuploidies (abnormal chromosomal abnormalities), which are associated with spontaneous abortions and refer to chromosomes 13, 15, 16, 18, 21, 22, X and Y.

In addition, molecular karyotype can detect abnormalities (deletions or duplications) in extremely small chromosomal regions, which can not be identified by the conventional karyotyping. Such chromosomal deficits are usually associated with various psychokinetic or mental syndromes.