What is Carrier Screening?
Carrier screening is a noninvasive (blood or saliva) test offered to all pregnant individuals or individuals considering pregnancy to find out if they have a higher chance to have a child with certain genetic conditions. Everyone “silently” carries genetic changes in their genes, even if you have a healthy family history. These genetic changes can also be called mutations or variants. Since carriers usually do not have any symptoms, testing blood or saliva is the only way to find out if you are a carrier.
Most conditions on carrier screening are recessive disorders. In these conditions, both biological parents must carry the same condition in order to have an at-risk pregnancy. The genetic condition affects a pregnancy or child only if both parents carry the same condition and both parents pass down their genetic change.
What are my Carrier Screening options?
- You have the option to decline carrier screening- regardless of your decision, newborn screening tests babies for some, but not all, of the conditions included on carrier screening panels. Newborn screening is a blood test completed on the baby after delivery to check for a number of disorders, some of which are included on carrier screening. All babies born in Texas are required to have two rounds of the newborn screen as many may not have any noticeable symptoms after birth. Abnormal newborn screens are reported to the pediatrician who helps coordinate confirmatory testing and treatment if needed.
- Standard carrier screening- this panel includes a few of the most common conditions, including cystic fibrosis (CF), spinal muscular atrophy (SMA), sickle cell anemia, and alpha thalassemia. If you are of Eastern European Jewish ancestry (also called Ashkenazi Jewish), Cajun, or French Canadian, you may benefit from additional screening for conditions such as Tay Sachs disease.
- Expanded carrier screening- this panel includes over 100 genetic conditions, including common and rare disorders. Expanded screening is more likely to find carriers of genetic conditions than basic screening, which gives a better risk assessment. However, less information may be available about rare conditions or rare genetic changes within our genes and there may be health implications for carriers of certain conditions. Families considering expanded carrier screening may benefit from meeting with a genetic counselor to further discuss this option in regards to their own personal and medical backgrounds.
What are the possible results from Carrier Screening?
- If your carrier screen is negative, your risk to have a baby with these specific genetic conditions is very low. Negative results do not eliminate your risk of having a baby with a genetic condition.
- If your carrier screen is positive for a recessive disorder, but the other parent’s screen is negative, the pregnancy is at low risk. Carrier screening is not 100% accurate, so we cannot eliminate the chance of having a baby with that condition. A genetic counselor can review the lowered chances of having a pregnancy or child with that condition after receiving these types of results.
- If both parents are carriers of the same recessive condition, there is a 25%, or 1 in 4, chance that both parents will pass on their genetic change and have a pregnancy or child with that condition. This means, carrier parents have a 75% chance they will not both pass on their genetic change and the baby would not have the condition.
What if my partner is not available for testing?
The most accurate information for the pregnancy requires both parents to be tested, and testing your partner can be performed in the doctor’s office or by shipping a saliva collection kit to your home. While carrier screening may still be useful when a partner is not available, we recommend discussing these benefits and limitations with a genetic counselor.
Should I have carrier screening?
Carrier screening is always optional. You can have carrier screening prior to becoming pregnant or during pregnancy. If you decide to have carrier screening, you may be tested first and then your partner will be tested only if your results are positive. Other times, both partners are tested at the same time. No test or combination of tests can screen for all genetic conditions and birth defects.
Where can I learn more Carrier Screening?
You can visit these helpful websites or you can call 713-486-9302 to schedule an appointment with a genetic counselor to discuss carrier screening.