PGT-M: preimplantation genetic testing for monogenic disorders

PGT-M, or preimplantation genetic testing for monogenic disorders, checks embryos created through IVF for a specific single-gene condition that runs in a family. It was previously known as preimplantation genetic diagnosis, or PGD. Because each embryo has to be tested in a laboratory, PGT-M is always carried out as part of an IVF cycle — even when a couple has no fertility problems of their own.

The aim is to identify embryos that have not inherited the faulty gene, so that only unaffected embryos are considered for transfer to the womb. In the UK, the Human Fertilisation and Embryology Authority (HFEA) has approved over 2,000 genetic conditions for PGT-M, making it an option for a wide range of inherited illnesses. If you are exploring your options, our genetic testing and counselling service can help you understand whether PGT-M might be relevant for your family.

PGT-M is designed for couples who know they carry, or are affected by, a serious single-gene disorder and want to reduce the chance of passing it on. This includes recessive conditions such as cystic fibrosis, sickle cell disease and thalassaemia, dominant conditions such as Huntington's disease, and X-linked conditions such as fragile X syndrome or Duchenne muscular dystrophy.

The level of risk depends on how the condition is inherited. When both partners carry the same recessive gene change — as happens with cystic fibrosis, where around 1 in 25 people in the UK are carriers — each pregnancy carries a 1 in 4 (25%) chance of an affected child. For a dominant condition such as Huntington's disease, a parent who carries the altered gene has a 1 in 2 (50%) chance of passing it on. A carrier screening test can confirm your carrier status before you decide on a pathway.

• You and your partner are both carriers of the same recessive condition, such as cystic fibrosis, sickle cell disease or thalassaemia
• One of you has, or carries the gene for, a dominant condition such as Huntington's disease
• You carry an X-linked condition such as fragile X syndrome or Duchenne muscular dystrophy
• You have already had a child, pregnancy or close relative affected by an inherited single-gene disorder
• A previous genetic test has identified the specific gene change in your family

PGT-M and PGT-A are often confused, but they answer different questions. PGT-M looks for one specific inherited gene fault that is already known to run in your family, whereas PGT-A (preimplantation genetic testing for aneuploidy) screens embryos for the wrong number of chromosomes — for example an extra chromosome 21, as seen in Down's syndrome — regardless of family history.

In short, PGT-M is targeted at a named single-gene condition, while PGT-A is a broader check on chromosome number. Some couples having IVF choose to combine both. You can read more about chromosome screening on our PGT-A page.

PGT-M is tightly regulated in the UK. The HFEA must approve each condition before it can be tested, weighing how serious the condition is and how likely it is to be passed on. This is why PGT-M can only be offered for conditions already on the HFEA's approved list, or for new conditions that a licensed clinic has successfully applied to add.

If the condition affecting your family is not yet on the approved list, a licensed centre can apply to the HFEA on your behalf for it to be considered. This safeguard ensures PGT-M is used consistently, and only for genuinely serious inherited conditions.

Reaching PGT-M usually follows a clear pathway. It often begins with carrier screening to identify the exact gene change involved, followed by genetic counselling to talk through your options, the implications for your family, and what the results could mean. Only then does treatment move to a licensed IVF centre, where eggs are collected, embryos are created, and a few cells are safely removed from each embryo and tested for the condition.

London Pregnancy Clinic supports the early, information-gathering part of this journey. We provide carrier screening and genetic counselling, and can help coordinate your onward care — but the IVF and embryo testing themselves are carried out at a specialist HFEA-licensed fertility centre, as we do not run an IVF laboratory. Some couples also choose confirmatory testing in a resulting pregnancy, such as non-invasive prenatal diagnosis (NIPD), for added reassurance.

If a single-gene condition runs in your family, the most helpful first step is understanding your risk and your options. Our clinical team offers genetic counselling and carrier screening in a calm, unhurried setting, so you can make decisions with clear, balanced information rather than under pressure.

We will explain how PGT-M works, whether your condition is likely to be eligible, and how to access a licensed centre should you decide to proceed. Throughout, our focus is on supporting you with evidence-based guidance tailored to your circumstances.

This information is intended for general educational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional — such as your GP or a genetic counsellor — for guidance specific to your individual circumstances.