Genetic carrier screening tests a person’s DNA to determine if he or she is at increased risk to have a child with certain genetic conditions. We all carry changes called variantsin our genes that can cause genetic conditions. Thankfully, most of these variants will never affect our own health or the health of our children.
Genetic carrier screening evaluates for conditions that are inherited in either an autosomal recessiveor X-linked manner. For conditions that are autosomal recessive, both the person contributing the egg andthe person contributing the sperm must carry variants in the same gene in order to have a child who is affected with that condition. For conditions that are X-linked, a female who is a carrier has an increased chance to have a child (especially a son) who is affected with that condition. Since men are not typically at risk for having children affected by X-linked conditions, many labs only screen women for X-linked genes.
Since being a carrier for one or more genetic conditions is very common, anyone who is pregnant or planning to become pregnant should consider having genetic carrier screening. The results can provide you with important information about your chances to have a child with certain genetic conditions. If your results indicate you are at increased risk to have a child with a genetic condition, you will have the opportunity to discuss your reproductive options with your physician (see question 13).
Yes. In fact, carrier testing was specifically designed to screen for genetic conditions that are unlikely to be detected due to a family history. Even if you have other children who are healthy, this cannot rule out the possibility you or your partner could be carriers for a genetic condition.
There are many options for genetic carrier screening. Some screen for only a few conditions, while others screen for hundreds of conditions. There is not one right answer for everyone. The conditions you are screened for depend on your personal preferences and the advice of your physician. Your ethnicity may also play a role in determining which conditions you should be screened for since certain genetic conditions are more common in specific populations. Keep in mind the more conditions you screen for, the more likely it is you will be a carrier for one or more of them.
The American College of Obstetricians and Gynecologists (ACOG) and the American College of Medical Genetics (ACMG) have published guidelines on carrier screening. Both organizations recommend carrier screening for cystic fibrosis and spinal muscular atrophy be offered to all individuals. ACOG recommends carrier screening for Fragile X syndrome be offered to women with a personal or family history of Fragile X-related disorders, intellectual disability, unexplained ovarian insufficiency, or an elevated FSH level before age 40. ACOG recommends screening for hemoglobinopathies such as alpha thalassemia, beta thalassemia, and sickle cell anemia be offered to those at increased risk based on ethnicity (e.g. African, Mediterranean, Middle Eastern, Southeast Asian, West Indian). Finally, ACOG and ACMG recommend carrier screening for cystic fibrosis, Canavan disease, familial dysautonomia, and Tay-Sachs disease be offered to all Ashkenazi Jewish individuals. In addition to those four conditions, ACMG recommends carrier screening for Fanconi anemia group C, Niemann-Pick type A, Bloom syndrome, mucolipidosis IV, and Gaucher disease be offered to Ashkenazi Jewish individuals as well.
Ideally, genetic carrier screening should be completed prior to pregnancy or the start of an IVF cycle. This gives you and your physician the most reproductive options in the event you are at increased risk to have a child with a genetic condition (see question 13).
You and your partner are welcome to be tested at the same time if you wish, but this is not necessary. Often the female partner will be tested first. If her genetic carrier screening is normal, the male partner does not need to undergo testing. However, if her screening is abnormal, we will recommend the male partner be tested at that point. Testing both partners at the same time is another approach and may be right for you if the wait time for results is a concern (see question 18).
It is important to keep in mind there are limitations when working with eggs or sperm from an anonymous donor. Many donors have had some form of genetic carrier screening, but the number of conditions tested varies widely. If your donor is a carrier for an autosomal recessive condition, we would strongly recommend the other individual contributing eggs or sperm have carrier testing for the same condition.
If your donor’s genetic carrier screening was normal, the question is more complicated. If you undergo genetic carrier screening that includes conditions for which your donor was not tested, you may find out you are a carrier for a condition that we do not have information on for the donor. Requesting additional testing on a donor can be time-consuming, costly, and may not be feasible if the donor is unreachable or does not consent to additional testing. Therefore, we recommend you discuss your options carefully with your physician or genetic counselor prior to having genetic carrier screening.
Not necessarily. If you have a family history of a specific genetic condition, it is important to meet with our genetic counselor to review your case. She can recommend the best genetic test to ensure you get the information you need.
In general, the same genetic test does not need to be performed twice as the results are not expected to change. However, there are many different types of genetic tests, and the technology is improving rapidly so it cannot be assumed that your previous genetic testing is the same as the current options we offer.
Please ensure our office receives copies of any previous genetic testing you have had. Your physician or genetic counselor can review the results to determine if there is any additional genetic testing that may be beneficial for you.
Most of the genetic conditions included on genetic carrier screening are rare. However, when you are screened for many conditions at once, it is quite common to learn you are a carrier for one or more of them. The more conditions you are screened for, the higher the chance you will be a carrier for at least one.
Typically not. You have two copies of most genes: one copy of each gene was inherited from your mother and one copy was inherited from your father. Carriers have one non-working copy of a gene, but their other copy is functioning normally. As a result, carriers for a recessive condition do not typically exhibit any symptoms. However, there are rare exceptions when being a carrier elevates a person’s risk for certain health issues. When we return your results, we will notify you if there are any implications for your own health that require follow up.
If the person contributing the eggs and the person contributing the sperm are both carriers for the same autosomal recessive condition, there is a 1 in 4 (25%) chance of having a child affected with that condition with each pregnancy. There is a 2 in 4 (50%) chance of having a child who is a carrier, but who is not affected with that condition. Finally, there is a 1 in 4 (25%) chance of having a child who is neither affected by nor a carrier for the condition.
If a woman is identified as a carrier of an X-linked recessive condition, she has a 1 in 2 (50%) chance to pass on that variant in each of her eggs. If the child is male, he will be affected with that condition. If the child is female, she may be mildly affected or an asymptomatic carrier; more rarely, a female may have symptoms that are equally severe to a male with the condition.
If you are at increased risk to have a child with a genetic condition, the results can help you plan and prepare. Your physician or genetic counselor can review all of your available reproductive options to help you make the choice that is best for you.
Patients who undergo IVF may choose to have preimplantation genetic testing (PGT), a process used to test embryos for a specific genetic condition. PGT allows your physician to select and transfer only those embryos that are not expected to be affected by the condition. If IVF with PGT is not right for you, genetic testing can also be performed during pregnancy through either chorionic villus sampling (CVS) in the first trimester or amniocentesis in the second trimester. CVS and amniocentesis both provide highly accurate genetic test results for the fetus allowing you to know if the condition was inherited or not. The results may be important for pregnancy management or medical planning for the birth of an affected child. Finally, some patients choose to use an egg or sperm donor who is not a carrier for the same condition in order to greatly reduce the chances of having an affected child.
No. Genetic carrier screening assesses your risk to have a child with a selectnumber of genetic conditions. A normal result greatly reduces the risk that your future children could be affected by those specific conditions, but it cannot eliminate the risk entirely. The small remaining risk is due to the possibility that there may be variants in your genes that can cause disease, but are not able to be detected with our current knowledge and technology. No genetic test is perfect.
It is also important to remember that every pregnancy has a background risk of approximately 3-5% to result in a child with a birth defect or genetic condition. This risk is always present, regardless of the screening performed.
There are a few things to consider. First, there is a cost associated with genetic testing, which may result in an out-of-pocket expense even with insurance. Second, results take approximately two weeks to return, and that wait can be frustrating for some patients. Ideally we like the results to be complete before you start an IVF cycle or try to conceive. Third, some individuals do not want the type of information provided by genetic carrier screening. For some, the information would cause anxiety. For others, they know they would not change their family building plans and would not pursue genetic testing of their embryos or pregnancy despite any results from genetic carrier screening. Fourth, genetic carrier screening cannot entirely eliminate the risk for genetic conditions in your future children (see question 14). Finally, although rare, genetic carrier screening may identify a genetic variant that has implications for your own health (see question 11). Patients may experience distress if their results indicate they have an increased risk to develop a health issue.
Many insurance plans provide coverage for genetic carrier screening, but specific benefits must be checked for each patient. The labs we work with can check your insurance benefits on your behalf and provide you with an expected out-of-pocket cost once your sample is received. You will have an opportunity to cancel your testing if the cost is too high. Many labs also offer reduced self-pay pricing if genetic carrier screening is not covered by your insurance plan.
A small blood sample (1-2 teaspoons) is the best sample for genetic testing and will be drawn in our office. In rare cases, we may submit a saliva sample instead of blood, but this is not preferred.
Results of genetic carrier screening typically take two weeks from the time your sample is received by the laboratory.
Our office will contact you by phone once your results are available. Typically, our genetic counselor calls out all carrier screen results so she can assist with any questions you may have at that time.
Any genetic variants you are found to carry are likely to be inherited. When someone is a carrier for a genetic condition, one of their parents is usually a carrier as well. Your full siblings have a 50% (1 in 2) chance of being a carrier for the same genetic condition(s) as you. More distant relatives such as aunts, uncles, and cousins would also be at increased risk to be carriers. For this reason, we strongly encourage you to share your carrier status with your family. If you need help explaining your results to your family, our genetic counselor will be happy to assist.
If your genetic carrier screening is normal, your results do not rule out the possibility that another family member (such as a sibling) could be a carrier for those genetic conditions. Your family members should still have their own genetic carrier screening performed if desired.
A positive (abnormal) result is highly accurate. False positives are rare in genetic testing. A negative (normal) result cannot completely eliminate the possibility you are a carrier for the conditions tested, but it does greatly reduce your risks (see question 14).
We strongly encourage all patients who have an abnormal genetic carrier screen to have an appointment with our genetic counselor. This consultation will ensure you fully understand the implications of your genetic test results. Our genetic counselor will also determine if there are any additional recommendations based on your test results or family history.