Trophectoderm biopsy (TEB): a safeguard for at-risk couples (W1)
Miscarriages and stillbirths take an extreme toll upon couples. Although miscarriages are relatively common, some patients are more affected than the average woman. Some couples also carry a serious genetic disease in their genetic material, which should on no account be passed on, for the benefit of the child. Or they simply do not get pregnant, despite several attempts. This is also a difficult situation. How does one treat someone who has such a genetic predisposition?
In these cases, preimplantation genetic diagnosis (PGD) can be used for couples wanting children. In order to potentially succeed in pregnancy after all, and the birth of a child. Trophectoderm biopsy (TEB) is one of the possible tests that can be done for couples wanting children, where there is a suspicion that both sides could pass on a genetic defect that could result either in miscarriage or stillbirth, or the embryo having a severe genetic disease.
How does it work?
Trophectoderm biopsy involves a biopsy of those cells of the embryo which develop into the placenta – that is, the "trophectoderm" or "trophoblast cells". The cells that develop into a child – that is, the "embryoblast" or "inner cell mass" – remain untouched during the test. The genetic makeup of these trophectoblasts is usually identical to that of the embryoblast. This means it is possible to comprehensively diagnose chromosomal maldistribution at a very early stage of pregnancy without manipulating the embryoblasts. The advantage of this examination is that the genetic material of the father can be checked at the same time.
First, several egg cells are artificially inseminated by means of ICSI. They are then cultivated for 5 days in the laboratory until they reach the blastocyst stage. The outer shell of the embryo is opened by means of a laser, and a capillary is used to remove up to five trophectoblast cells. The biopsied embryos are then cryopreserved – that is, frozen – to be implanted by the doctor, if one is shown to not have abnormal genetic findings. The extracted cells are examined in one of our laboratories.
It can happen that a not completely intact embryo does not survive the cryopreservation. There is also a residual risk of about 2 to 3 percent that a genetic defect is nevertheless present, despite a trophectoderm biopsy with no abnormal findings. Because genetically modified cells can exist next to genetically unmodified cells and thus remain undetected (genetic mosaic).
For whom does a trophectoderm biopsy make sense?
Austria has exact stipulations on when a trophectoderm biopsy may be performed. Couples wanting children can resort to pre-implantation diagnosis in the following cases:
- A couple has had at least three unsuccessful embryo transfers (for example, due to an impermeable fallopian tube and subsequent failure of the egg to implant in the uterus), and it is suspected that this was due to a genetic cause.
- At least three miscarriages or stillbirths have been detected, most likely due to the genetic disposition of the child.
- Due to the genetic disposition of at least one parent, there is a risk of a miscarriage or stillbirth or the child having a serious genetic disease. And approval must be obtained from the Scientific Committee for Gene Analysis and Gene Therapy (WAGG).
We therefore only perform pre-implantation diagnosis in accordance with the above-mentioned legal guidelines and after comprehensive genetic counselling.
Pre-implantation diagnostics (PID)
Another examination method of pre-implantation genetic diagnosis is polar body diagnosis (PBD). A more single-focused review of the genetic situation of the egg than the trophectoderm biopsy. Because it gives no information about the health of the sperm cell. In this check, only the biopsy of the polar bodies on fertilised eggs is examined, and they undergo an indirect genetic analysis. Polar bodies are created during maturation of the egg and are not needed for further development.
In our fertility centres, our doctors are happy to advise you and clarify together with you whether a form of pre-implantation genetic diagnosis is an option for you. Please do not hesitate to contact us!