Genetic carrier screening

Overview

Understand which inherited conditions your children could be at risk of, and make informed choices. Many couples use genetic carrier screening to find out which medical conditions their future children might inherit. The team at Minerva Women's Healthcare can explain the benefits and limits of carrier screening, and also offers guidance on noninvasive prenatal testing (NIPT). We provide this care with the warmth and respect you deserve. Schedule a visit today for pre-pregnancy screening or antenatal care by calling our office or booking your appointment online.

At a glance

Carrier screening is a genetic test that shows whether you or your partner carry a gene for certain inherited conditions
Carriers usually have no symptoms and often do not know they carry the gene
It is best done before pregnancy, but can also be done during pregnancy
NIPT is a blood test in pregnancy that screens for certain chromosome conditions, with no risk to the baby
Testing is optional, and we will help you decide what is right for you

What is carrier screening?

Carrier screening is a genetic test that shows whether you or your partner carry a gene for a specific inherited disorder. A carrier has one copy of a gene for a condition. Carriers usually have no symptoms, or only mild ones, and often do not know they carry the gene. When carried out before or during pregnancy, carrier screening can show your chance of having a child with a genetic disorder.

How are conditions inherited?

Many of these conditions are recessive. If both parents are carriers of the same recessive gene, there is a 1 in 4 chance with each pregnancy that your child inherits the gene from both parents and has the condition. There is a 1 in 2 chance that your child will be a carrier, like the parents, and a 1 in 4 chance of inheriting neither copy. If only one parent is a carrier, the child will not have the condition, but there is a 1 in 2 chance of being a carrier.

Sickle cell disease is a common example. A person with sickle cell trait (for example, AS or AC) is a carrier. If both parents carry the trait, there is a 1 in 4 chance of a child with sickle cell disease in each pregnancy. Carrier screening is especially useful for couples who do not know their sickle cell status.

What types of carrier screening are there?

Targeted screening: Tests for specific conditions that are more common in your ethnic group or family. For example, sickle cell disease and other haemoglobin conditions are common in people of African descent, and Tay-Sachs disease is more common in people of Eastern or Central European Jewish, French-Canadian and Cajun descent.

Expanded carrier screening: Checks for many conditions, sometimes up to 100 or more, regardless of your background or family history. These may include:

Cystic fibrosis
Fragile X syndrome
Sickle cell disease and other conditions affecting the red blood cells
Tay-Sachs disease
Spinal muscular atrophy (SMA)

Your doctor can explain each type, and help you decide which is right for you and your partner.

What if both of us are carriers?

If you are both carriers, you have options, which we will talk through without pressure. Depending on the condition, these may include testing during pregnancy, planning care for a baby who may have the condition, or fertility options that reduce the chance of passing it on. A genetic counsellor can help you understand what it means for your family.

What is NIPT?

Throughout pregnancy, a small amount of your baby's DNA, which comes from the placenta, circulates in your blood. NIPT, or noninvasive prenatal testing, takes a sample of your blood and analyses this DNA to screen for certain chromosome conditions. Because it needs only a blood sample from you, it does not put your baby at risk.

NIPT is most often used to screen for:

Trisomy 21 (Down syndrome)
Trisomy 18 (Edwards syndrome)
Trisomy 13 (Patau syndrome)

NIPT can also show extra or missing copies of the sex chromosomes, X and Y. NIPT is a screening test, not a diagnosis. A "high-risk" result needs to be confirmed with a diagnostic test, such as amniocentesis, and a normal result does not completely rule out a condition. We will explain what the result means for you.

Is screening right for me?

Screening is a personal choice. Benefits include knowing your risks, preparing, and making informed decisions. Limits include that no test checks for every condition, a negative result does not remove all risk, and results can sometimes cause worry. We will discuss the pros and cons and respect whatever you decide.

Common questions

When should I have carrier screening?

Ideally before you become pregnant, so you have more options. If you are already pregnant, it can still be done, and sooner is better.

Does my partner need to be tested too?

Often yes. Many conditions only affect a child if both parents are carriers, so testing both of you gives the clearest picture.

If I have a healthy family, do I still need screening?

Possibly. Most carriers have no family history, because the gene can pass silently through generations.

Is NIPT safe?

Yes. It is a blood test and does not affect your pregnancy.