- Reproductive options for at risk couples
- What is prenatal diagnostic testing?
- What is preimplantation genetic diagnosis (PGD)?
Being diagnosed with an inherited condition or being told you are a carrier of a specific genetic mutation may cause significant lifestyle changes such as the decision of having children. This is because there is a risk of passing the same genetic mutation to future generations and depending on the mode of inheritance, the mutation may or may not cause disease in your child. A genetic counsellor is able to help you through this difficult decision by providing information on the exact risk of passing the condition based on your genetic result and discuss about the available reproductive options.
Reproductive options for at risk couples
If genetic testing shows that a couple have an increased risk of having a child with an inherited eye condition, there are different options and choices available which include:
- Remain childless
- Going ahead with a natural pregnancy with no intervention, with the understanding that the future child is at a risk of being affected with the genetic condition
- Undergo prenatal diagnostic testing during pregnancy (PND) with the option to voluntarily terminate an affected pregnancy
- In vitro fertilisation (IVF) with preimplantation genetic diagnosis (PGD) to identify unaffected embryos and re-implant into the mother’s womb
- Conception through gamete (egg or sperm) or embryo donation
What is prenatal diagnostic testing?
Prenatal diagnostic testing is carried out to assess whether or not a developing foetus has a specific genetic condition. This is normally offered if there is an increased risk of the baby being affected with the condition.
This is usually done by obtaining a small sample of the developing baby’s cells through one of two ways:
- Chorionic villus sampling (CVS): Usually carried out in the first trimester between 11-14 weeks by taking a small sample of cells from the placenta
- Amniocentesis: Usually performed in the second trimester (15-20 weeks) by collecting a small sample of amniotic fluid
Both procedures are considered invasive and have a small risk of causing miscarriage, which is less than 1%.
If an affected pregnancy is identified, the couple will have to make a decision as to whether to undergo a voluntary termination or to continue with the pregnancy.
What is preimplantation genetic diagnosis (PGD)?
Preimplantation genetic diagnosis, also known as preimplantation genetic testing, is a special type of in vitro fertilisation (IVF) technique to ensure the birth of an unaffected child. This is carried out through the following approach:
- An embryo is created outside of the body by IVF using the eggs and sperm from the couple
- The embryo is then tested for the specific genetic condition in the family
- Only unaffected embryos are re-implanted into the womb with the hope that it will result in a normal birth
In the UK National Health Service (NHS), a couple would first need to be seen by their local clinical genetics service who would go through all the reproductive options and confirm their eligibility based on a list of criteria which include:
- There must be at least 10% risk of the couple conceiving a pregnancy affected by a serious genetic condition
- They must have received genetic counselling from a clinical geneticist or a registered genetic counsellor
- At the time of treatment, the female partner must be under 40 years of age and have a body mass index (BMI) of more than 19 and less than 30
- They must both be non-smokers
- There must be no unaffected child from the current relationship