Preimplantation genetic diagnosis: information for patients
Last Reviewed 1/09/2016
The following gives you information about preimplantation genetic diagnosis (PGD). PGD is a reproductive technique used along side in vitro fertilisation (IVF) by couples at risk of passing on serious genetic condition. This page tells you more about what PGD is and how and why it is done. This information is designed to be used alongside the discussions you have with your health care professionals and help you to ask the questions that are important to you.
What is preimplantaton genetic diagnosis?
PGD is a technique that enables couples with a particular inherited condition in their family to avoid passing it on to their children. The process helps potential parents prevent the birth of a child with a serious genetic condition. PGD is used when a couple has a known risk of passing on a genetic abnormality and diagnostic testing is performed on an embryo to determine if it has also inherited the abnormality.
PGD involves the use of assisted reproductive technology (ART). Eggs are obtained and fertilised through in vitro fertilisation (IVF). Once fertilised, the embryos develop for 5-6 days and then a number of cells are removed from each embryo. The genetic material (DNA or chromosomes) within these cells of the embryo is then tested for the genetic or chromosomal abnormality. An unaffected embryo is then transferred to the woman’s uterus to implant. If successful, the procedure will result in pregnancy and the child should not be affected by the condition for which it was tested.
Who can use preimplantation genetic diagnosis?
Couples who request PGD are at risk of passing on a serious genetic condition to their children. Parents may have the condition themselves or be carriers of the condition. They may already have a child affected or they may have experienced the loss of a child or pregnancy affected with the condition.
Couples generally considered for PGD include:
Carriers of a serious* autosomal recessive condition: For carriers of an autosomal recessive condition, there is a 1 in 4 (25%) risk of each pregnancy delivering an affected child.
Carriers of a serious autosomal dominant condition: For carriers of an autosomal dominant condition, there is a 1 in 2 (50%) risk of each pregnancy delivering an affected child.
Couples with inherited chromosome disorders.
Couples with a family history of serious sex-linked disorders: Couples with a family history of a sex-linked disorder have a 1 in 4 (25%) risk of each pregnancy delivering an affected child (half of all male children).
Therefore, PGD may be recommended if:
- you or your partner has a family history of a serious genetic condition and/or
- you and your partner already have a child with a serious genetic condition and/or
- you and your partner have had a number of pregnancy terminations because your baby had a serious genetic condition.
*In this section we have used the word ‘serious’ a lot. This is because the HFEA must find that a condition is ‘sufficiently serious’ to allow PGD in relation to it.
Which conditions can be diagnosed using preimplantation genetic diagnosis?
PGD is available for three broad categories of conditions including:
Single gene defects for which PGD testing is available.
Chromosomal abnormalities, including inversions, deletions, aneuploidy (an abnormal number of chromosomes), and translocations (where a piece of one chromosome either becomes attached to another chromosome or swaps places with a segment from another chromosome).
Sex-linked conditions, for which it is not yet possible to test for the specific genetic mutation, in which case they test for sex rather than mutation.