Embryo testing

embryo Embryo testing through preimplantation genetic diagnosis or ‘PGD’ has been authorised on a discretionary basis for a number of years by the Human Fertilisation and Embryology Authority (HFEA). The Human Fertilisation and Embryology Act 2008 has enshrined the legal parameters in law for the first time. The new legal rules, which came into force on 1 October 2009, put certain decisions into a legal context rather than being at the HFEA’s discretion.

The law states that a treatment licence from the HFEA which permits embryo testing may only do so for the following purposes:

Embryo testing to exclude abnormalities

PGD may be used to try to select an embryo that is free of a gene, chromosome or mitochondrion abnormality. This might be an abnormality that causes miscarriage or stillbirth, in which case the purpose of the testing is to give the best chance of a successful pregnancy. Alternatively, it might be an abnormality that would affect any child born, in which case the purpose of the testing is usually to try to choose an embryo for treatment that is free of the disorder in question.

The law allows testing for this latter category (i.e. for inheritable conditions) only if:

there is a particular risk of the embryo having the abnormality (i.e. if. there is a family history or one of the parents is known to be a sufferer or carrier) and
the HFEA is satisfied that ‘the abnormality carries a significant risk that a person with the abnormality will have or develop a serious disability, illness or medical condition’. This is a double test: the condition being tested for must be considered sufficiently serious, and there must be evidence that the abnormality being tested for significantly increases the chances of a person suffering from the condition.

Embryo testing: which conditions are considered sufficiently serious?

The requirement for the abnormality to carry a significant risk of creating a serious condition means that PGD is only allowed where the condition being tested for is considered sufficiently serious. PGD could not, for example, be used to exclude minor complaints or genetic defects that might be considered purely cosmetic.

Click here for more information from the HFEA about the conditions for which PGD is currently licensed to test.

Embryo testing: sex selection as a means of excluding abnormalities

Where a serious condition/ illness cannot be tested for directly, but affects one sex significantly more than the other, PGD may also be used for sex selection. This gives parents the opportunity to put back embryos only of the unaffected sex, and so to reduce the chance of their child suffering from the condition.

These are the only circumstances in which sex selection is permitted in the UK. Sex selection for non-medical reasons is prohibited (both through PGD and other methods such as sperm sorting).

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Embryo testing: ban on preferring affected embryos

Once embryos have been tested for an abnormality, an affected embryo cannot be ‘preferred’ over an unaffected embryo.

This does not mean that, if you test for a condition, you are completely barred from being treated with any embryos found to carry it. If, for example, your embryos were tested and all were found to have the condition in question, then (subject to discussions, medical advice, counselling etc) the rules on embryo testing would not prohibit you from proceeding with treatment.

However, the rules do not allow you to use PGD to deliberately choose an embryo that is affected by an abnormality.

Embryo testing: saviour siblings

PGD may also, where licensed, be used to help select an embryo that is a tissue match for a sibling. This might apply to you if you have an older child who suffers from a serious medical condition that could be treated by cord blood, bone marrow or other tissue, and you are unable to find a suitable donor.

The law allows you to use PGD to select an embryo to produce a sibling who will be a tissue match for your sick child. However, there are restrictions. The law makes it clear that embryo selection can be used only for tissue donation: a child may not be conceived to act as an organ donor for his/her sibling.

Embryo testing: suspected embryo mix ups

Where a question has arisen about who are the biological parents of an embryo, PGD may also be used to establish biological parentage.

If an embryo mix up comes to light before treatment (which will hopefully be extremely rare), this allows parentage to be tested before the embryo in question is implanted in the intended mother, which may be preferable to allowing the embryos to perish or proceeding with treatment where there is uncertainty.

Storage of tested embryos

Under the current law, any embryo (including those that have undergone PGD testing) may be stored for the normal statutory storage period of ten years. Extended storage of embryos which have undergone testing may be available, depending the medical circumstances (click here for further information).