Our Correspondents
What if you could find out your odds of having a child with
a genetic disorder before you even got pregnant? Modern testing makes it
possible. With at-home tests, it’s easier than ever to get screened.
Doctors usually recommend this step for parents-to-be who
have a higher risk of passing on certain diseases, like cystic fibrosis. And
because of these screening tests, the number of people who have some disorders,
like Tay-Sachs disease, has gone way down.
But what if you’re not considered high risk? Should you
check your genes before you get pregnant? Your doctor or a genetic counselor
can help you decide.
How does genetic tests work?
Many genetic disorders happen when a person has two bad
copies of a gene, one from each parent. If you have only one faulty copy, you
won’t have any symptoms of the condition, but you are a ‘carrier’ for it. Your
baby will be born with the disorder only if both you and your partner pass the
bad gene to him.
•To do a genetic carrier screening, also called
preconception testing, your doctor will take a small sample of your saliva or
blood during a checkup before you get pregnant. She will send the samples to a
lab for testing. If you use an at-home kit, you’ll take the sample and send it
to a lab yourself. The tests look closely at your DNA for genes that are linked
to certain diseases. Standard screening tests check for: Cystic fibrosis
•Fragile X syndrome
• Blood disorders such as sickle cell disease
• Tay-Sachs disease
• Spinal muscular atrophy
Newer tests, called expanded genetic carrier screenings, can
also find flawed genes for more than 400 other disorders, some of which are
rare and have few treatments. Universal testing and at-home screening kits have
opened the door for people of all risk levels to check their genes before pregnancy.
Who needs screening?
Your doctor will probably recommend a test for you and your
partner if either of you is at a higher risk of being a carrier. This could
happen if:
•A disorder runs in your family.
•You belong to an ethnic group with a high risk of genetic
diseases, including:
•Ashkenazi Jewish (Tay–Sachs disease and others)
•African (sickle cell disease)
•Mediterranean and Southeast Asian (thalassemia)
If you are not in one of these groups, think about what the
results of a screening might mean for you before you decide to get one.
Essence of genetic carrier screening
A test can’t tell you without a doubt whether your child
will have a disorder before you’re pregnant. Results from a genetic screening
test only help doctors more accurately predict your chances of passing problem
genes to your children.
Still, there are some pros and cons to having the test. Some
of the positives:
• It can find unknown problems. Many of the flawed genes
these screening tests find aren’t linked to your race, ethnicity, or family
history. You might never know you or your partner carries them. If you know
your risk, you can make better informed decisions about your family.
• It can provide answers about your family history. The
results can help you figure out if you’re in a high-risk group, especially if
you don’t know your family history or if you come from a multiethnic
background.
• The test itself is easy. Tests you get after you’re
already pregnant, called prenatal tests, can have some risks for you or your
baby. Taking a blood or saliva sample before you’re pregnant is quick and harmless.
Some cons:
• Results may be incorrect. No test is 100 per cent
accurate. Yours could say you are not a carrier for a gene when you really are.
On the flip side, very rarely, a result could say you carry a faulty gene when
you do not. These incorrect results, or the possibility that your tests might
be wrong, can be stressful when you are making choices about having a baby.
• You cannot always know how the genes will affect your
baby. Even if you know there is a chance your child will inherit flawed genes,
you may not be able to tell if she will show symptoms of the disorder, how
severe they will be, or if they will get worse over time, depending on the
disease.
What Else to Consider
Genetic carrier screening tests can give people important
information, but they are not right for everyone. Think things through before
you make your decision:
• How might the results affect me? Will knowing your chances
of passing down a genetic disorder make you more or less worried during
pregnancy?
• How might the results affect my family? Sharing (or not
sharing) your results with family members who may also be affected by the
information could cause tension.
• What will my next steps be? Think ahead about how you
might handle news of your results. It may help to talk with a genetics
counselor, who can help you think about the possibilities and your options. Ask
your doctor to refer you to someone.
You and your partner might also consider in-vitro
fertilization (IVF). With this method, doctors can combine the egg and sperm in
a lab and check the embryo for any gene problems before you carry it in your
womb. It’s called pre-implantation genetic screening. A genetics counselor can
help you decide if it’s a good option for you.
