Genetic ambulatory office
Examination of the embryo
As part of methods of assisted reproduction, it is possible to carry out a genetic examination and the selection of embryos arising in the test tube before transfer to the uterus and implantation, so-called pre-implantation.
The method of examination is based on the conclusions of the genetic consultation. Pre-implantation examinations may be either targeted on diseases already present in the family or on random genetic changes of the external environment or age of parents.
First, a cell or several cells are separated from the embryo – a so-called biopsy – by an embryologist on the 3rd or 5th day after sperm fertilization.
Embryo biopsy on the 3rd day
Chromosomes are examined in a single cell (blastomere) of the 3rd-day embryo. The result of the examination may be available within 48 hours.
Embryo biopsy on the 5th day
Chromosomes are examined in 3 to 5 cells of the 5th-day embryo (blastocysts). Embryos are subsequently frozen and, in the case of normal results, transferred to one of the other cycles. The result of the genetic examination is usually available within one month.
Two basic types of pre-implantation examinations are differentiated:
PGD (Pre-implantation Genetic Diagnosis) - a targeted embryo examination to exclude hereditary diseases in the family, when one or both partners are carriers for a given genetic disease. This may be a chromosomal error as well, such as a monogenic hereditary disease (amongst the most common are cystic fibrosis – CF, spinal muscular atrophy – SMA, haemophilia and muscular dystrophy).
In the case of gender-related diseases (e.g., haemophilia), it is also possible to select embryos of the sexes that are not at risk of disease. Otherwise, embryo selection by sex is not possible by law. From the viewpoint of the disease in question, only healthy embryos are embedded in the uterus, thereby minimizing the risk of the infant's birth or the need to terminate the pregnancy early.
PGD can also be used in cases where, for ethical reasons, prenatal diagnosis is not used (e.g. for diseases that manifested only in adulthood, such as congenital tendencies towards tumour diseases).
A PGS (pre-implantation genetic screening) examination of an embryo to exclude newly arising chromosome defects in parents without genetic disorders. These are disorders of the number of chromosomes (aneuploidy) that occur randomly in the maturing of ova and sperm or during embryo development. The aim of this examination is to select a genetically healthy embryo for transfer, thereby increasing the chance of successful implantation of the embryo in the uterus, reducing the number of necessary embryo transfers and lowering the risk of spontaneous miscarriage or suffering a chromosomal error. We can at the same time clarify the causes of IVF failure.
PSG is recommended especially in women:
- age 35 years or older
- after repeated miscarriages or after unsuccessful assisted reproduction
- with the occurrence of chromosomal errors of a foetus in previous pregnancy or an already existing disabled child
- after oncological treatment from the past