Carrier Genetic Testing (CGT), sometimes called carrier screening or expanded carrier screening, can help you understand whether you carry genetic variants that could potentially be passed on to your children.
Most people who carry a genetic condition are completely healthy and have no symptoms. You may be a carrier without knowing it, even if there is no history of the condition in your family.
For some inherited conditions, a child is only affected if they inherit a relevant genetic variant from both biological parents. Testing both partners can therefore identify couples who may have an increased chance of having a child affected by a particular inherited condition.
At Manchester Fertility, our specialist team can help you understand whether carrier testing could be appropriate for you, explain your results and discuss your reproductive options if you are both found to carry a variant for the same condition.
Carrier Genetic Testing looks for specific genetic variants that can cause inherited conditions.
A carrier usually has one altered copy of a particular gene and one working copy. In many conditions, having one altered copy does not cause the person to have the condition themselves.
However, if both biological parents carry a variant affecting the same autosomal recessive condition, there can be a chance that their child inherits an altered copy from each parent.
For every pregnancy involving two carriers of the same autosomal recessive condition, there is typically:
These probabilities apply to each pregnancy independently. They do not mean that one in every four children will necessarily be affected.
The NHS and NHS England Genomics Education Programme use cystic fibrosis as an example of this inheritance pattern.
You don't need to have a family history of a genetic condition to be a carrier.
Many inherited conditions are recessive, meaning that a person can carry a disease-causing variant without knowing it. As a result, a genetic condition can sometimes appear in a family unexpectedly.
Carrier testing may give you important information about your reproductive choices before pregnancy.
For some people, testing provides reassurance. For others, finding out that both partners carry a variant for the same condition allows them to consider their options before trying to conceive.
These options can include:
The right option will depend on the particular condition, your circumstances and your personal preferences.
The purpose of CGT isn't to tell you whether you will or won't have a healthy baby. Instead, it provides information about specific inherited conditions so that you can make informed reproductive decisions.
Carrier testing can be considered by anyone planning to have children, particularly where there is a known family history of an inherited condition.
It can be particularly relevant if:
If you, your partner or a close relative has a known genetic condition, targeted genetic testing may be appropriate.
Where a specific genetic variant is already known within a family, testing for that particular variant may be more informative than a broad carrier screening panel.
Couples who are biologically related, such as first cousins, can have a higher chance of carrying the same recessive genetic condition.
Genetic counselling can help explain the implications and determine what testing may be appropriate.
Genetic screening can be particularly relevant when donor gametes are being used.
UK fertility clinics have responsibilities regarding donor screening, but the HFEA states that expanded carrier screening is not currently mandatory for UK gamete donors, and there is no national UK guidance specifically for expanded carrier screening.
At Manchester Fertility, genetic carrier screening forms part of our donor treatment pathways where applicable. Our current treatment information includes Genetic Carrier Screening for relevant sperm providers and recipients using partner sperm.
You don't need to have fertility problems to consider carrier testing.
Some people choose to have genetic carrier screening before trying for a baby because they want to understand more about their reproductive genetics in advance.
Carrier testing is usually straightforward. Depending on the specific test, genetic material may be collected using a blood or saliva sample.
The laboratory analyses your DNA for genetic variants associated with the conditions included in the test.
Your results will then indicate whether you:
No relevant variant was detected for the conditions tested.
A relevant variant was identified, but this does not usually mean that you have the condition yourself.
In some circumstances, further testing or specialist interpretation may be required.
Being a carrier is usually not a diagnosis of disease.
If you are found to carry a variant associated with a recessive condition, the next step will depend on the condition and your reproductive circumstances.
If your partner is not a carrier of a relevant variant for the same condition, the risk of having an affected child may be substantially reduced, although your child may still have a chance of being a carrier.
If both biological parents are carriers of the same autosomal recessive condition, further discussion with a genetics professional can help you understand the risks and available reproductive options.
For example, NHS guidance explains that when both parents carry a cystic fibrosis variant, each pregnancy has a 25% chance of being affected, a 50% chance of producing an unaffected carrier and a 25% chance of producing a child who is neither affected nor a carrier
Finding that you and your partner both carry variants associated with the same condition does not mean you cannot have a healthy family.
It means you have additional information that may be important when considering your reproductive options.
Your options may include:
You may choose to conceive naturally and have diagnostic testing during pregnancy.
Tests such as chorionic villus sampling (CVS) or amniocentesis can be used to diagnose a range of genetic conditions during pregnancy.
The HFEA recognises prenatal testing as one of the options available to people at increased risk of passing on a serious inherited condition.
Pre-implantation Genetic Testing for Monogenic disorders (PGT-M) can be used to test embryos created through IVF for a specific inherited genetic condition.
Embryos are tested in the laboratory, and embryos that are suitable for transfer can then be selected according to the specific genetic testing strategy.
Importantly, PGT-M is different from carrier screening.
CGT tests the prospective parents.
PGT-M tests embryos created through IVF for a specific genetic condition.
The HFEA currently states that PGT-M can be used for more than 2,000 approved genetic conditions, although individual conditions must meet the relevant regulatory requirements.
Some people may consider donor sperm or donor eggs if there is a significant risk of passing on an inherited condition.
Donor treatment involves its own medical, genetic, legal and counselling considerations, all of which should be discussed with your fertility clinic.
Genetic testing is a personal decision.
Some people choose to have the information so they can make decisions before pregnancy. Others may prefer not to undergo testing.
There is no single right decision.
Our role is to give you clear, balanced information so that you can make the decision that is right for you.
CGT does not require IVF.
You can have carrier screening whether you're planning to conceive naturally or considering fertility treatment.
However, if testing shows that both biological parents carry variants associated with the same serious inherited condition, IVF with PGT-M may be one of the reproductive options available to you.
If PGT-M is being considered, the process is more complex than routine carrier screening because the laboratory needs to establish a testing strategy for the specific genetic condition and family.
The HFEA explains that PGT-M must be performed as part of an IVF treatment cycle, even where the couple does not otherwise have fertility problems.
The terminology surrounding genetic testing can be confusing.
Looks at embryos created through IVF for a specific genetic condition caused by a change in one or more genes.
It is generally considered when there is a known risk of passing a serious inherited condition to a child.
Looks at embryos created through IVF to assess chromosome number.
It is different from CGT and PGT-M and does not test embryos for a specific inherited single-gene condition.
The HFEA describes PGT-A as testing embryos for abnormalities in the number of chromosomes, whereas PGT-M is used for specific monogenic conditions.
Although genetic testing can provide valuable information, it is important to understand its limitations.
A carrier screening panel only tests the genes and variants included within that particular test.
Not every disease-causing variant can necessarily be detected.
Some genetic variants may have uncertain significance or may require additional interpretation.
Autosomal recessive conditions are only one type of inheritance. Other conditions can be inherited in different ways, including X-linked inheritance.
For example, the NHS England Genomics Education Programme explains that the reproductive risks associated with X-linked conditions differ from those associated with autosomal recessive conditions.
Genetic information can have implications for you, your partner and other family members.
For this reason, genetic counselling or specialist clinical advice can be an important part of the process, particularly when a significant genetic risk is identified.
Genetic screening is particularly relevant when donor sperm or donor eggs are used because the genetic background of the donor and recipient can form an important part of treatment planning.
The HFEA requires fertility clinics to carry out appropriate donor screening, but expanded carrier screening is not currently a mandatory requirement across UK fertility clinics.
Manchester Fertility has dedicated expertise in donor treatment and clinical genetics. Our Lead in Clinical Genetics, Dr Peter Kerecsenyi, oversees the clinic's work in genetic diagnostics, including carrier screening and pre-implantation genetic testing.
Where carrier screening is recommended or forms part of your treatment pathway, our team can explain what is being tested and what the results may mean for you.
At Manchester Fertility, we understand that genetic testing can feel daunting.
Our aim is to make the process as clear and straightforward as possible.
We can help you understand:
We take your individual circumstances into account rather than taking a one-size-fits-all approach.
Our clinical genetics expertise means that genetic testing is considered as part of your wider fertility picture, alongside your reproductive history, age, ovarian reserve and other relevant factors.
Genetic testing is an increasingly important part of modern reproductive medicine.
At Manchester Fertility, our team combines fertility medicine with specialist knowledge of reproductive genetics to help patients make informed decisions about their family-building options.
Our Lead in Clinical Genetics, Dr Peter Kerecsenyi, has specialist training in clinical genetics and oversees genetic diagnostics at Manchester Fertility, including carrier screening and pre-implantation genetic testing.
Whether you're planning a pregnancy, undergoing fertility treatment, using donor sperm or eggs, or have concerns about a genetic condition in your family, we can help you understand your options.
Peter oversees the rapidly changing field of genetic diagnostics, including carrier screening and pre-implantation genetic testing.
Usually, no. For many recessive conditions, carriers have one altered copy of a gene and one working copy and do not have symptoms of the condition themselves.
However, the implications depend on the specific condition and genetic variant, so your result should always be interpreted in its appropriate clinical context.
It depends on the circumstances and the type of testing being undertaken.
If one person is found to carry a variant for an autosomal recessive condition, testing their reproductive partner may help determine whether there is an increased chance of having an affected child.
If your partner is not a carrier of a relevant variant for the same recessive condition, the chance of having a child affected by that particular condition is generally much lower.
Your child may, however, inherit your variant and become a carrier.
If both biological parents carry variants associated with the same autosomal recessive condition, there is typically a 25% chance in each pregnancy of having an affected child.
You can discuss options such as natural conception with prenatal testing, IVF with PGT-M where appropriate, or donor treatment with a fertility specialist and genetics professional.
No.
Carrier Genetic Testing normally tests the DNA of the prospective parent or parents.
If you become pregnant and need to establish whether the pregnancy is affected by a particular genetic condition, prenatal diagnostic testing may be considered.
If you're considering IVF because of a known genetic risk, PGT-M can be used to test embryos for an approved specific condition.
No test can guarantee that a future child will be completely free from every genetic or medical condition.
Carrier screening looks at particular genes and variants included in the test. It provides information about specific inherited conditions rather than a complete prediction of a child's future health.
Some targeted genetic and carrier tests are available through NHS services when there is an appropriate clinical indication.
For example, NHS screening and testing pathways exist for conditions including sickle cell disease and thalassaemia, while carrier testing for specific conditions may be offered where there is a family history or known risk.
Expanded carrier screening is different. The HFEA currently states that there is no national UK guidance specifically for expanded carrier screening and that it is not a mandatory requirement for UK fertility clinics or gamete donors.
No.
CGT identifies whether you or your partner carry certain genetic variants.
PGT-M tests embryos created through IVF for a specific genetic condition.
They can be complementary: carrier testing may identify an increased reproductive risk, while PGT-M may subsequently be considered where appropriate.
No. Carrier testing does not require IVF.
You can have carrier screening before trying naturally, during fertility treatment or as part of donor treatment.
IVF may become one of the options to consider if both biological parents are found to carry variants associated with the same serious inherited condition and PGT-M is appropriate.
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