Before you fall pregnant: preconception genetic tests for mom and dad
Posted on 5 February 2019
From timing to finances, there is so much to consider before trying for a baby. One consideration you’re probably not even aware of is the impact your genetics may have on your children.
You and your partner may not be affected by a genetic disease, but you may be carriers. This means you are at risk of passing a genetic condition on to your child.
Thankfully, a series of tests are available to help determine that risk. Called preconception carrier screening, this is testing offered to couples before they fall pregnant and covers a range of common genetic conditions.
“The aim of these tests is to see whether healthy potential parents are carriers of certain genetic conditions and whether there is a risk of passing these conditions on to their future children,” says Chantelle Scott, a genetic counsellor at Mediclinic Panorama.
According to Scott, there are two kinds of tests available. A comprehensive screen which covers almost 300 different conditions, or a targeted test that identifies diseases specific to a person’s family history and ancestry.
Who is at risk?
“The most common condition to consider is cystic fibrosis for all population groups. If you are of Jewish decent, Tay Sachs, Gaucher disease and Canavan disease should be considered and sickle cell anaemia if you are of African descent,” she says.
Targeted screening is also available for Fragile X Syndrome. All the conditions tested for can be fatal for a child or cause lifelong health problems.
With carrier screening becoming cheaper and more accessible, there is good reason to get tested, especially if your background puts you into one of the at-risk groups. In fact, the American College of Obstetricians and Gynecologists (ACOG) recommends that all women be offered carrier screening.
However, Scott suggests seeking the help of a genetic specialist to guide your decision. “A genetic counsellor can help ensure you understand exactly what the tests are looking for and how to interpret the results. This will ensure you know your risks and options when planning a pregnancy,” she says.
If you’re a carrier…
It’s important to understand that everyone carries some kind of genetic mutation, she says. “Most people who have the comprehensive test done are found to carry one of the conditions screened for,” she explains.
Being a carrier usually does not have any impact on you, and only becomes a problem if your partner carries a genetic change in the same gene or for the same condition. “If you are both found to be carriers, there is a 25% chance that you will have a baby with the condition,” says Scott.
Depending on the condition identified, couples may consider pre-implantation genetic diagnosis (PGD). This involves having in-vitro fertilisation and testing the embryos so that only unaffected embryos are selected and implanted.
Alternatively, couples may choose to conceive naturally and do further testing during the pregnancy. “Some conditions respond to treatment after birth and knowing ahead of time helps prepare you and your healthcare team,” says Scott.
As the field of genetic testing grows, it is fast becoming a useful guide for potential parents. “It is a useful way of gathering as much information about your risks as possible in order to make informed decisions when planning a pregnancy,” says Scott.