Infertility is an issue that is becoming more common, with new data indicating that one in six people in Canada may be experiencing difficulty conceiving. Are you wondering what the links are between genetics and infertility? Here are several situations where genetic counselling could change your care.
Genetic causes of infertility
Although infertility is often complex and involves many factors, it is now known that up to 20% of cases could have a genetic origin. Basic assessments (ovarian reserve and spermogram) can identify problems in the quality and/or quantity of the egg or sperm cells and lead to a recommendation of targeted genetic testing to assess for genetic causes that may impact your management and have an impact on the health of your future children.
Genetic causes of repeated miscarriages
For some couples, the difficulty is not conceiving, but carrying a pregnancy to term. While it is unfortunately common for any woman trying to conceive to experience pregnancy loss in the first trimester, it is less common to have multiple miscarriages. Once other identifiable causes have been ruled out, the possibility of a genetic cause remains to be investigated.
- In the majority of cases, there is an accidental chromosomal abnormality, which occurs randomly at the time of fertilization, with a risk that increases with maternal age. A test of the fetal tissue, called an analysis of the products of conception, can identify these abnormalities.
- In 2 to 4% of cases, one of the two biological parents has a balanced and silent chromosomal rearrangement (e.g. translocation) that is responsible for a recurrent unbalanced chromosome abnormality. This type of rearrangement can be identified with a test called a karyotype and genetic counselling is highly recommended to discuss the risk for future children if an affected pregnancy were carried to term, as well as the reproductive options.
The importance of medical, family, and obstetric history and ethnic origin
During the first few visits to a fertility clinic, you will be asked about your personal medical history and family history. If any element of your health or that of your relatives appears to be associated with a risk of carrying or passing on a genetic condition, your doctor will refer you for genetic counselling to review your history in detail and assess whether you are eligible for certain tests to help clarify your risks.
The risk of passing on silent genetic conditions to children
All conceptions carry a risk of passing on silent genetic conditions. In some fertility clinics, expanded carrier screening is offered to all couples in preconception, but could be particularly indicated when two reproductive partners are related (consanguinity), if a family history is poorly known, or if one comes from a population with more specific genetic risks due to a founder effect. If a genetic risk is identified between two partners, reproductive options will be made available.
Genetic risk when using an egg or sperm donor
Among the many care options in fertility clinics, the use of a third party (egg or sperm donor, surrogate) to achieve conception is not uncommon, and allows infertile couples, same-sex couples and single people to access parenthood. If your clinical and/or personal situation requires the use of an egg or sperm donor to conceive and you are in the process of choosing, genetic counselling can help you understand the risks of transmitting silent genetic conditions to your children. Private genetic testing could also be offered here to assess the risk of transmission of several hundred genetic conditions.
Preimplantation genetic diagnosis (PGT-A, PGT-M, PGT-SR)
Preimplantation genetic diagnosis involves taking a biopsy of a few cells from the outer layer of an embryo on day 5 of its development following in-vitro fertilization and then performing genetic testing, with the aim of selecting the embryos that have the best potential to result in a healthy pregnancy.
- In the case of PGT-A (preimplantation genetic testing for chromosomal abnormalities), this could in some cases increase the pregnancy rate following embryo transfer and reduce the overall risk of miscarriage.
- In the case of PGT-M and PGT-SR (preimplantation genetic testing for monogenic diseases and structural chromosomal rearrangements), only patients known to have a particular genetic risk will have access and the testing is customized to their specific situation to assess that risk.
In both cases, pre-test genetic counselling can help you in making a decision on whether or not to choose this option, which is not guaranteed to result in a healthy child and has many limitations. Post-test genetic counselling is highly recommended to help you understand the results, your options for transfer and how to prioritize embryos based on the results.
As you can see, genetics can have more than one impact on your fertility follow-up! Our team of genetic counsellors who are experts in reproductive genetics is available at any time along your journey to help you in your decisions, explain the issues and support you in managing your health and that of your family in the future.