The donor by law has to be 18 to 35 years in age, of normal intelligence, in good health and with no past or family history of severe physical, mental or genetic disease. All donors are required to undergo a medical examination and details are asked about their personal, medical and family history. A donor may not be accepted whenever a risk is envisaged to her, her existing children or to the future child.
All donors are carefully screened according to current guidelines and best practice.
Which screening tests are performed on the donor?
All prospective egg donors have an analysis performed of their chromosomes.
In addition, we routinely test for cystic fibrosis. The screening will be performed for only the 12 commonest gene mutations in the Caucasian and Northern European populations. These mutations account for 85% of all varieties known to medicine to date. Exclusion of these mutations reduces the risk of being a carrier for cystic fibrosis to about 1% for these populations. In other population’s e.g. Asians, the incidence of cystic fibrosis is much lower than that among Caucasians. Whilst all 12 mutations known to be common in the Caucasian and Northern European populations are excluded, the risk of being a carrier among the Asian donors cannot be accurately determined.
In addition, wherever appropriate additional screening tests may be applied. For example:
- East European, South Asian and Middle Eastern donors are screened for Thalassaemia.
- Donors with African descent are screened for Sickle cell disease.
- Jewish donors are screened for Tay Sach’s disease.
It is very important for the recipient couples to understand that not all known gene mutations are or can be possibly screened for and even after screening of some, there may be others for the same disease that are either uncommon or are not yet known. Hence the likelihood of developing these illnesses can be minimised with this screening but cannot be completely eliminated.
SCREENING FOR INFECTIONS:
- All egg donors are screened for HIV, hepatitis B and C.
- Syphilis: All egg donors are screened for syphilis
- Cytomegalovirus (CMV): This virus commonly infects people and in normal circumstances gives a minor flu like illness. However it can become activated in pregnancy and can harm the baby. It is a very common infection in the normal population and many of us are exposed to it during our lifetime. We screen all donors and use CMV negative donors only for CMV negative recipients. On the other hand, CMV positive recipients can have gametes from both negative and positive donors.
What is the risk of a congenital abnormality?
The risk of a congenital abnormality after treatment using donor eggs is believed to be the same as for natural conception in a normal couple that is approximately 1 – 2%. The risk of having a child with Down’s syndrome and other similar abnormalities, miscarriage or a still birth as a result etc is that in the donor’s age group in the normal population. GP’s and those responsible for the obstetric care (obstetricians and midwives) routinely advise the recipient couples about prenatal diagnostic tests as appropriate.
How are the Donors matched to the Recipients?
Physical characteristics such as height, weight, body build, hair colour, complexion, eye colour, race and blood group etc are recorded. We try to provide an acceptable match. There are fewer donors and detailed matching for physical characteristics can prove difficult. Matching for ethnic origin and rhesus blood group is always performed. Exceptions are always discussed with the recipient couple in advance.