Polar body diagnostics are used to detect maternal hereditary diseases during artificial insemination. Polar body diagnostic testing takes place before the egg is fertilized. The discard of the unfertilized cell has much in common with the discard of an actual embryo in moral terms.
What is polar body diagnosis?
In polar body diagnostics, polar bodies are taken from both maternal and paternal material to rule out genetic defects before fertilization. Polar body diagnostics is a procedure of prefertility diagnostics. The term “prefertilization diagnostics” describes genetic testing methods that are intended to detect genetic defects during artificial insemination even before the egg is fertilized. In polar body diagnostics, individual elements of the retrieved egg cell are thus examined for defects before zygote formation. Preimplantation diagnostics, which are also molecular genetic tests, are to be distinguished from prefertilization diagnostics. These procedures determine whether an embryo is implanted into the uterus after in vitro fertilization has already taken place. Since ethical questions arise in this context, preimplantation genetic diagnosis is not permitted in all countries. In Austria, for example, preimplantation genetic diagnosis is prohibited. Prefertilization diagnostics and polar body diagnostics are still permitted, since no actual embryos are discarded if there are findings.
Function, effect, and goals
In vitro fertilization offers the possibility of pregnancy to couples with fertility problems and an unfulfilled desire to have children. In vitro fertilization products are also known as embryos in a jar. In this procedure, the egg is fertilized outside the female body and implanted into the uterus after fertilization. In order to exclude genetic defects before fertilization, polar bodies are taken from both the maternal and paternal material. The polar bodies are formed during meiosis. They adhere to the oocyte, contain little cytoplasm and are equipped with a simple set of chromosomes. Polar body diagnostics in the context of in vitro fertilization includes not only the collection, but also the human genetic examination of the polar bodies. In this way, genetic defects can be detected and the egg can be discarded before fertilization if there are abnormal findings. The procedure is mainly carried out before the fusion of maternal and paternal material, as diagnostics on the already fertilized egg was originally not permitted for ethical reasons. In this way, polar body diagnostics can be used to detect, for example, incorrect distributions of the chromosome set even before fertilization. Chromosome mutations such as translocations can also be detected by means of this examination. In addition, segregation detection of maternally passed on monogenetic diseases is possible within the scope of polar body diagnostics, which is provided by the so-called polymerase chain reaction. This procedure is a method of in vitro amplification of hereditary substances. If the polar body diagnostic tests do not show any abnormalities, the first cell division is awaited. This results in an embryo, which is transplanted into the mother’s uterus if there are no abnormal findings. If there are abnormal findings instead, the egg can be discarded before an embryo actually develops. Because of the increased risk due to age, the examination of the chromosome set is particularly relevant in older women in order to exclude aneuploidies such as trisomy 21. In addition, polar body diagnostics enables the detection of maternal hereditary diseases of the dominant and X-linked form in the Mendelian inheritance. Paternal disease factors, however, cannot be comprehensively detected by polar body diagnostic examinations. Thus, polar body diagnostics does not provide a reliable exclusion of genetic defects. Preimplantation diagnostics, on the other hand, can also detect paternal hereditary diseases, so that pre-implantation diagnostic procedures are superior to polar body diagnostics in this respect. However, the rejection of an already fertilized egg, as it must be for pre-implantation diagnostics, is considered ethically irresponsible by many people.
Risks, side effects and dangers
Ethical issues are highly relevant to the field of fertilization medicine. Governmental guidelines define the framework within which fertilization is considered responsible. In Germany, this framework is also known as the Embryo Protection Act. Due to the introduction of the Protection Act, preimplantation genetic diagnosis was only permitted in moderation for a long time, as it was associated with the rejection of actual embryos and thus disregarded the Embryo Protection Act. For this reason, prefertilization and polar body diagnostics were pushed forward in Germany. Since 2011, however, preimplantation genetic diagnosis has been approved for appropriate indications throughout Germany. Scientifically, preimplantation diagnostics are superior to polar body diagnostics, so that polar body diagnostics have only been used to a limited extent since 2011. Neither the one nor the other procedure is associated with physical risks and side effects for the mother or father. However, the result of both diagnostics can confront a couple with psychological stress during family planning. Therefore, couples should go into the examinations with as stable a constitution as possible. In the case of abnormal findings, the question arises as to whether the mother and father wish to discard the egg at all. Unsuccessful fertilizations in the past have often put a strain on relationships and in individual cases even ended them. The same applies to complications during fertilization, as they can occur with hereditary diseases and thus possibly come to light through polar body diagnostics. Couples should therefore be aware in advance of how stressful the diagnostic procedure can be for their relationship. Indications for a polar body diagnostic examination can be known hereditary diseases in the family. The age of the mother can also be an inducement for polar body diagnostics, since the risk of mutations increases after a certain age.
