Carrier Screening Before Pregnancy

Why you should opt for carrier screening before trying for pregnancy.

Carrier screening analyzes DNA to identify your chances of having a child with a genetic disorder. Whilst carrier screening can be done during pregnancy, Lama Elkhoury from Sema4 speaks with Dreaming of Baby about the importance of testing prior to conceiving.

Daniela: Good afternoon and welcome to Dreaming of Baby! We have with us Lama Elkhoury from Sema4, joining us for our segment on what should be considered before trying for baby. Today’s focus is carrier screening tests. It’s a pleasure to have you with us today Lama; before we start with our discussion, it would be great if you could introduce yourself to our readers.

Lama Elkhoury, MS, CGC: Hello and thank you for having me today. I am a Certified Genetic Counselor who has been in practice for over 10 years. I am currently the Director of Genetic Counseling Services at Sema4, a health information company that is a venture of Mount Sinai Health System and features a full-service genetic testing laboratory. I previously held several clinical positions where I was interfacing with individuals who were already pregnant or attempting to achieve pregnancy.

What is carrier screening testing?

Daniela: Thank you for this introduction Lama, to start with our discussion as well as to provide clarifications to our readers, what is carrier screening testing?

Lama Elkhoury, MS, CGC: Carrier screening is a test that analyzes your DNA to see if you are a carrier of a genetic variant (or change) that could cause an inherited disease in your children. Medical experts such as the American College of Obstetricians and Gynecologists (ACOG) recommend that carrier screening be offered to all women who are pregnant or planning for pregnancy. Carrier screening plays an important role in family planning and is ideally performed before you are pregnant. This gives you the most reproductive options if you test positive as a carrier for a genetic condition. For those who are already pregnant, carrier screening is still important to help them better understand their reproductive risk and prepare for a healthier future for their family.

Daniela: Thanks for this overview Lama. You note that this screening should be ideally done before pregnancy. Is this something that can be done via an OBGYN?

Lama Elkhoury, MS, CGC: Yes, an OBGYN or even a General Practitioner can order this test.

Should I do a carrier screening test?

Daniela: That’s very good to know. Are there any factors which make such testing more of a must?

Lama Elkhoury, MS, CGC: Carrier screening is recommended for everyone who is planning a pregnancy in the near future regardless of ethnicity, age or family history. The types of conditions that are usually tested for are such that a completely healthy couple who have no incidence of a genetic disorder in their family may actually harbor a genetic change that when passed down to a child could cause disease to manifest.

Daniela: Connected to this then, you noted above that the American College of Obstetricians and Gynecologists recommend carrier screening for all women who are pregnant or planning a pregnancy. To clarify then, is this testing for women only or it’s something done as a couple?

Lama Elkhoury, MS, CGC: Carrier screening panels include disorders that are classified as “autosomal recessive” this means that both the mother and the father need to be “carriers” for the same disorder for there to be an increased risk to their child. Couples may choose to be tested concurrently; or may choose to begin screening the mother and then only perform testing on the father if she is identified to be a carrier.

Lama Elkhoury, MS, CGC: Since most carrier screening is ordered by OBGYNs on women, their reproductive partners can sometimes face challenges being tested. At Sema4, we decided to ease the burden on the reproductive partners by developing a sample collection kit that can be completed at home and then submitted to our laboratory for testing.

“Carrier screening is recommended for everyone who is planning a pregnancy in the near future regardless of ethnicity, age or family history.” Lama Elkhoury, MS, CGC

What happens once carrier screening has been done?

Daniela: Thank you for clarifying. For the couple who has had testing done, what would be the next step for them and what would be the role of a genetic counselor in this regard?

Lama Elkhoury, MS, CGC: If the result is negative, it can be very reassuring; however, no carrier screen is 100% perfect and a genetic counselor can help explain any residual risks that still remain despite such a result. If the result is positive for a genetic disorder in the woman, her reproductive partner would need to be screened for that same genetic disorder. If he, too, is also a carrier for the same genetic condition, a genetic counselor can help explain 1) the disorder in question 2) the risks of their child potentially being affected with the disorder and 3) the reproductive options that are available to the couple. It is important to note that some carrier screening panels also include some disorders that are classified as “X-linked”: this means it is sufficient for the mother alone to be a carrier for there to be an increased risk to their child. If a woman is positive for an X-linked disorder, testing her reproductive partner is not warranted, and a genetic counselor can speak with her about her reproductive risks.

Daniela: This is very interesting to know; when you speak of residual risk – what kind of risks would these involve?

Lama Elkhoury, MS, CGC: Depending on a person’s ethnicity they can be quoted a baseline risk for being a carrier of a specific genetic condition. For example, a person of Caucasian ancestry has approximately a 1 in 25 chance of being a carrier for a disorder called Cystic Fibrosis. If a Caucasian person undergoes carrier screening for Cystic Fibrosis, with a detection rate of 94%, a negative result decreases their odds of being a carrier to 1 in 401 (this is their residual risk for still being a carrier in spite of a negative result). Another example is Sickle Cell disease in the African American population. Individuals of African American ancestry start with a baseline risk of 1 in 12 for being carriers for Sickle Cell disease. Carrier screening for Sickle Cell disease has a detection rate of greater than 99%, so a negative result would confer a residual risk of 1 in 1,100.

Daniela: Thanks for clarifying. It’s been a very interesting discussion on a very important subject. On a final note, what would be that one piece of advice that you’d always share with a couple who are thinking of trying to conceive?

Lama Elkhoury, MS, CGC: As a Genetic Counselor, I am a big advocate for patient education and awareness, so I would encourage couples who are about to embark on this exciting journey to try to get as informed as possible from the many outlets available today (information is power!). It is important to recognize, however, that there can be a lot of misinformation on the internet and one should confirm accuracy with a medical professional.

Daniela: Thank you for sharing this sound advice Lama, it was a pleasure discussing this subject with you.

Click here to read more about carrier screening.

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