Genetic disorders: Screening and management

Genetic disorders are conditions caused by abnormalities in a person’s DNA that often arise when both parents carry a mutation in the same gene. While many people carry genes linked to certain disorders without experiencing symptoms, these genes can be passed on to their children.

This article underlines the importance of genetic screening, the available tests, and how fertility treatments like IVF can manage genetic risks.

Why is genetic screening important for couples panning to have children?

Genetic screening is crucial for identifying the risk of passing genetic disorders to offspring. For couples considering starting or expanding their family, genetic screening helps to detect genetic disorders early, enabling couples to make informed choices about conception and providing essential information about any potential risks to their children.

Couples should consider genetic screening if they have a family history of genetic conditions or if they have experienced recurrent miscarriages or unexplained infertility. Additionally, people from ethnic groups with a higher prevalence of specific genetic disorders should undergo testing. Genetic screening is also recommended for couples planning to use assisted reproductive technologies like in vitro fertilisation (IVF).

What genetic screening tests should I consider?

In the UK, a range of genetic screening tests are offered as part of standard preconception care. Broadly, genetic screening can be divided into carrier screening and more targeted tests for known genetic conditions.

Carrier screening is a common type of preconception testing. It involves testing to determine whether you carry mutations in genes linked to recessive disorders, which only manifest if both parents pass down the same genetic mutation to their child.

Some of the most commonly-screened genetic disorders include: cystic fibrosis, spinal muscular atrophy, Tay-Sachs disease, sickle cell anaemia, and thalassemia. Fragile X syndrome is frequently included as well.

For couples with a family history of specific genetic conditions, additional testing will be tailored to detect mutations known to run in their families. Conversely, expanded carrier screening panels are also available, covering hundreds of genetic conditions, for couples with no known family history of genetic disorders.

What happens if both my partner and I are carriers of the same genetic disorder?

If both you and your partner are found to be carriers of the same genetic disorder, your child has a 25% chance of inheriting the condition, a 50% chance of being a carrier, and a 25% chance of not being affected. While high-risk genetic mutations can be alarming, there are several options to help you navigate this scenario.

In some cases, couples may choose to proceed with natural conception (being understanding of the risks involved) and undergo prenatal testing, such as chorionic villus sampling (CVS) or amniocentesis, to assess the baby’s genetic health during pregnancy.

Other times, couples may opt for IVF with preimplantation genetic testing (PGT) to allow the selection of embryos free of the disorder. Using donor eggs, sperm, or embryos from people who aren’t carriers of the genetic disorder is another viable option. These options ensure the embryo doesn’t inherit the disorder.

How do fertility treatments like IVF with PGT help in managing genetic risks?

For couples facing significant genetic risks, IVF combined with PGT can significantly reduce the risk of transmitting genetic conditions to your child.

The process involves retrieving eggs from the ovaries and fertilising them with sperm in a laboratory to create embryos. Once these embryos reach a specific stage of development, a few cells will then be biopsied and tested for genetic disorders. This will allow fertility specialists to identify embryos that are free of genetic mutations, which will then be selected for transfer into the uterus for implantation.

There are 3 main types of PGT:

• PGT-A (aneuploidy): Screens for chromosomal abnormalities, such as Down syndrome.
• PGT-M (monogenic disorders): Tests for single-gene disorders, such as cystic fibrosis or Tay-Sachs disease.
• PGT-SR (structural rearrangements): Identifies structural rearrangements in chromosomes.

Although this process may involve additional costs and steps, it offers many couples reassurance by helping ensure their children have the healthiest possible start in life. If you have questions about genetic screening or concerns about inherited conditions, reach out to a fertility specialist for personalised advice and support.