Polar body diagnostics

The polar body diagnosis (PKD) enables a genetic examination of the removed egg as part of an artificial fertilization (assisted reproduction). This examination is a pre-fertilization diagnostic that is carried out on the egg before fertilization is complete, i.e. H. occurs before zygote formation . This diagnosis is still permitted in some countries, such as Austria, where pre-implantation diagnosis is prohibited.

method

By in vitro fertilization , the egg is fertilized outside the body. Before the maternal and paternal pronuclei have merged, the two polar bodies are usually removed and examined genetically. Within this narrow time frame - which resulted from the original prohibition of pre- implantation diagnosis (PGD) - the following examinations can be carried out up to the fusion of the pronuclei ( syngamy ) and thus the formation of an embryo:

• Chromosome set maldistributions
• Translocations
• Detection of segregation of a maternally inherited monogenic disease using PCR

If the results are normal, fertilization can be completed and the first cell divisions await and the resulting embryo implanted in the uterus.

The examination of the chromosome set is carried out in particular with regard to the aneuploidies (e.g. trisomy 21 ) that increase with maternal age . In the case of monogenic diseases, the detection of the pathogenic allele in the polar body can provide information on whether the healthy allele is present in the egg cell. However, this assumes that the genetic disease to be examined is known in the mother. Thus, according to the Mendelian inheritance, only dominant and X-linked hereditary diseases inherited on the maternal side can be recognized; In the case of recessive ones - if the father knows a pathogenic allele - either a 25 percent risk can be concluded or all egg cells that carry the mutation can be discarded. Since only the maternal genome can be detected, none of the paternal factors are detectable. In this respect, PGD is technically superior to PKD in many ways.

Application and security

Polar body diagnosis has been promoted in Germany mainly because the Embryo Protection Act has so far only permitted pre-implantation diagnosis to a very limited extent. A review from 2008 shows that in women who have an increased risk of aneuploidy due to their older age, the probability of implantation of transferred embryos increases slightly and the miscarriage rate decreases after a polar body diagnosis. A significant increase in the birth rate could not be proven.

As of December 2011, the legal situation regarding PGD in Germany changed so that it is essentially allowed for those indications. Science will show to what extent there are still medically justified advantages of polar body diagnostics over pre-implantation diagnostics.

literature

• Peter Propping : The perfecting of polar body diagnostics. A consequence of the Embryo Protection Act. In: Dtsch Arztebl. Volume 105, No. 11, 2008, ISSN  0012-1207 , p. 189 ( online ).
• K. van der Ven, M. Montag, H. van der Ven: Polar body diagnostics - a step in the right direction? In: Dtsch Arztebl. Volume 105, No. 11, 2008, ISSN  0012-1207 , pp. 190–196 ( full text ).

Individual evidence

1. ↑ see: Diagnostics of monogenic diseases. In: K. van der Ven, M. Montag, H. van der Ven: Polar body diagnosis - a step in the right direction? In: Dtsch Arztebl. Volume 105, No. 11, 2008, ISSN  0012-1207 , pp. 190–196 ( full text )
2. ↑ K. van der Ven, M. Montag, H. van der Ven: Polar body diagnosis - a step in the right direction? In: Dtsch Arztebl. Volume 105, No. 11, 2008, ISSN  0012-1207 , pp. 190–196 ( full text )
3. ↑ November 21, 2011: Law regulating pre-implantation diagnostics (Preimplantation Diagnostics Act - PräimpG). from No. 58 of November 24, 2011, p. 2228; on-line

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !