Genetic Testing in Fertility: Which Tests and What They Answer

Genetic testing in fertility answers different questions depending on what is being tested. Testing the parents can identify a cause of infertility or a condition that could be passed on. Testing embryos, through PGT, checks embryos before transfer. The distinction matters because the evidence supporting each is different: testing for a condition already identified in a family is well founded, whereas screening embryos for chromosome number as a general measure is not supported for most patients. Before agreeing to any test, ask what it would change about your treatment.

Tests on the parents

Karyotype

Examines the number and structure of a person's chromosomes. It is generally offered after recurrent miscarriage, since a balanced rearrangement in either partner can cause repeated losses while causing the carrier no symptoms, and in men with very low or absent sperm counts.

Y chromosome microdeletion testing

For men with azoospermia or a severely low count. Which region is affected bears on whether surgical sperm retrieval is likely to succeed, so the result informs a decision rather than simply labelling the cause. It also has implications for a son conceived through ICSI, who would inherit the same deletion.

Carrier screening

Checks whether prospective parents carry variants for recessive conditions such as cystic fibrosis or thalassaemia. Carriers are usually healthy, so this is not something a family history reliably reveals. Where both partners carry the same variant, that changes what options are discussed.

Tests on embryos

All require IVF, since there has to be an embryo in the laboratory to test.

• PGT-M tests for one specific single-gene condition already identified in the family.
• PGT-SR tests for a known structural chromosome rearrangement.
• PGT-A screens chromosome number. It is the only one of the three that is a screen rather than a targeted test, and it is the one whose benefit is disputed. The HFEA rates it red for improving the chance of having a baby for most patients and notes it may reduce that chance by reducing the embryos available for transfer.

Our articles on the differences between the three and on whether to have PGT-A go into detail.

What has actually improved

The technology has genuinely advanced. Sequencing is faster, cheaper and more detailed than it was, and carrier screening now covers far more conditions from a single sample.

Better detection is not the same as better outcomes, though, and that gap is where most of the confusion sits. A test that identifies more findings is only useful if the findings change what happens next. For PGT-M and PGT-SR they clearly do. For PGT-A the evidence is that they often do not.

Questions worth asking

• What specifically would this test change about my treatment?
• What does a normal result rule out, and what does it not?
• What happens if the result is inconclusive?
• Is genetic counseling available alongside the result?
• What does it cost?

Genetic results can carry implications for other family members and for future children, which is why counseling matters more here than with most tests.

We at Millennium IVF Clinic will advise which testing applies in your case. You can arrange a consultation with our team, and our article on genetic causes of infertility covers the conditions themselves.

Frequently asked questions

Should every couple have genetic testing?

No. Testing follows an indication: recurrent miscarriage, azoospermia, a family history, or membership of a group with a higher carrier rate for a specific condition.

Does a normal genetic test mean my embryos will be healthy?

No. Each test answers one question. A normal karyotype does not exclude single-gene conditions, and no test excludes everything.

Does genetic testing improve IVF success?

It depends which test. PGT-M and PGT-SR avoid transferring embryos with a known condition. For PGT-A, the HFEA rates it red for improving the chance of having a baby for most patients.

Will testing tell me why we cannot conceive?

Sometimes. Genetic causes account for a proportion of cases, and a great many have no identifiable genetic cause at all.