Family history and genetic counselling

A genetic assessment starts with a family history: conditions in relatives, previous pregnancy losses, and whether the partners are related by blood. Genetic counselling helps people understand the risks and benefits of a test, what its possible findings mean, and how relatives may be affected. The American College of Medical Genetics and Genomics (ACMG) advises that counselling about carrier screening be given both ahead of the test and once the report is back.

Who it is generally relevant to

Couples where either partner, or a relative, has a genetic condition
Couples who are related by blood
Couples with recurrent pregnancy loss, after an individual assessment
Men with no sperm or a very low sperm count (see male infertility)
Anyone with an earlier genetic report that needs explaining

Carrier screening

Many inherited conditions are recessive: a person who carries one altered copy of a gene is usually healthy. When both partners carry an altered copy of the same gene, each pregnancy has a one-in-four chance of being affected (MedlinePlus). Carrier screening is a test, usually on blood or saliva, that looks for these silent changes.

The ACMG recommends offering carrier screening to everyone who is pregnant or planning a pregnancy, using a defined panel of conditions, and considering a broader screen when the partners are related as second cousins or closer. Screening before pregnancy leaves the widest range of choices.

If both partners carry the same condition, the options can include testing during pregnancy or IVF with PGT-M, which tests embryos for that specific condition. Genetic counselling helps couples weigh them.

Karyotype

A karyotype looks at the number and structure of a person's chromosomes, using a blood sample. A balanced rearrangement, such as a translocation, usually causes no health problems for the person who carries it, but it can lead to pregnancies with missing or extra chromosome material. For couples with recurrent pregnancy loss, the ESHRE guideline does not recommend routine karyotyping of both partners, but suggests it after an individual assessment of risk; see recurrent pregnancy loss.

Exome sequencing

Exome sequencing reads the protein-coding parts of all the genes, about 1 percent of the genome, where most known disease-causing changes are found (MedlinePlus). It is used in specific situations, usually when an inherited condition is suspected in a family and simpler tests have not explained it.

Testing embryos

Embryos created through IVF can be tested before transfer: PGT-M for a specific inherited condition, and PGT-A for the number of chromosomes. The UK regulator, the HFEA, rates PGT-A red for improving the chance of having a baby for most patients, because it often reduces the number of embryos available for transfer, while high-quality evidence shows that it reduces the chance of miscarriage.

Risks and limits

Most genetic tests need only a blood or saliva sample. Their limits matter more. A negative carrier screen lowers the chance of being a carrier but does not remove it, and a panel covers a defined list of conditions, not every condition. Exome sequencing can find changes whose meaning is uncertain, and sometimes changes linked to a different condition from the one being investigated (incidental or secondary findings). Testing can also reveal unexpected information about family relationships. That is why counselling comes before any test and again once the report is back.

Questions worth asking your doctor

Which conditions does this screen cover, and which does it not?
Would the finding change any decision we make?
If a change of uncertain meaning is found, how will it be followed up?
Should relatives be told, and how?

Common questions

Should every couple have carrier screening?

The ACMG recommends offering it to everyone who is pregnant or planning a pregnancy, ideally before pregnancy. Whether to have it is a personal decision, best made after counselling about what the screen covers and what you would do with the findings.

Is PGT-A useful for everyone having IVF?

No. The HFEA rates PGT-A red for improving the chance of having a baby for most patients, although high-quality evidence shows that it reduces the chance of miscarriage. Your doctor can advise whether it is relevant in your situation.

How long do genetic tests take?

It depends on the test and the laboratory. The NHS notes that a report can take weeks or months, and that further tests are sometimes needed.

What does a variant of uncertain significance mean?

It is a change in a gene whose effect on health is not yet known. It is not a diagnosis, and its meaning may become clearer as knowledge grows; your doctor can advise how it should be followed up.

Evidence basis: This page is based on guidance from the ACMG, ESHRE, the HFEA, the NHS and the US National Library of Medicine, and the studies they cite; where the evidence is limited, the page says so.

References

Screening for autosomal recessive and X-linked conditions during pregnancy and preconception: a practice resource of the American College of Medical Genetics and Genomics (ACMG), Genetics in Medicine (ACMG) (2021) — doi:10.1038/s41436-021-01203-z
If a genetic disorder runs in my family, what are the chances that my children will have the condition?, MedlinePlus Genetics, U.S. National Library of Medicine (2021) — medlineplus.gov
What are whole exome sequencing and whole genome sequencing?, MedlinePlus Genetics, U.S. National Library of Medicine (2021) — medlineplus.gov
Genetic and genomic testing, NHS (2023) — nhs.uk
Guideline on the management of recurrent pregnancy loss, European Society of Human Reproduction and Embryology (ESHRE) (2023) — eshre.eu
Pre-implantation genetic testing for aneuploidy (PGT-A), Human Fertilisation and Embryology Authority (HFEA) (2023) — hfea.gov.uk

Written and reviewed by Dr. Ghina Shami, Consultant, Reproductive Medicine and Infertility · 13 October 2026 · How these pages are prepared

Genetic testing and carrier screening