Genetic testing may be useful in cases of severe sperm problems, advanced female age (over 38 years), previous anomalous infant births, two or more unsuccessful in vitro fertilization treatments. The possibility of pregnancy after healthy transfer of a genetically normal embryo to the womb and the possibility of healthy ongoing pregnancy may be increased following genetic tests in IVF.
In recent years, various techniques such as PGT (preimplantation genetic diagnosis), array CGH (24 chromosome screening) and NGS (next generation screening) have become able to extract embryos with chromosomal problems.
The purpose of this genetic screening is to detect and isolate chromosomally abnormal embryos and to transfer embryos which are normal into the uterus. For example, when 6-8 eggs are obtained and with microinjection 5 eggs are fertilized and if 3 embryos reach the blastocyst stage which are 5th day embryos, it is possible to biopsy these three embryos for genetic investigation and select normal embryo without chromosomal problem. When the embryo with normal chromosomes is transferred into the uterus, the likelihood of obtaining a healthy pregnancy will increase.
Whether PGT, array CGH or NGS techniques is used for genetic screening of embryos is decided based on the age of woman and previous treatments and previous pregnancies of the couple. Again, it would be right to choose the NGS technique, which allows for the most precise and extensive examination in the presence of certain genetic diseases.
Today, many genetic diseases can be diagnosed at the embryo stage. For example, diseases such as thalassemia, SMA muscle disease, hemophilia, Down syndrome can be detected in the embryo and the transfer of the anomalous embryo into the womb is thus prevented.
If the couple has a genetically ill child, it is possible to determine the absence of this genetic disorder in the second child. In such treatments, blood samples are taken from the mother, the father, and the child with the genetic disorder in a preparation phase (called set-up). This stage is 1-2 months on average, and after completion of this preparation phase, IVF treatment is started.
The method of genetic screening of embryos in IVF treatment is recommended in couples with advanced maternal age (after 39 years of age), couples who previously had two or more failed infertility treatments, couples who have had two or three previous abortions, and children with genetic disease.
The possibility of these tests being incorrect is expressed as 1-2%. For this reason, it is recommended to perform close follow-up and screening tests during pregnancy in couples who achieved pregnancy with this method.
In summary, genetic methods in IVF treatment are performed in special cases. In the near future, it may be possible to apply those techniques routinely in IVF treatment at reduced costs which might enable the spread of genetic techniques.
Banu Kumbak Aygun, M.D., Professor
Gynecology & Obtetrics