Blog

This is a transcription of a portion of a Healthful Woman podcast.

Danielle’s Question

A long-time listener, Danielle, asked us this question on a recent Mailbag episode:

“I’m almost 16 weeks, and recently found out that I’m a carrier for cystic fibrosis. None of my family had knowledge of it running in our bloodline. So, it was quite a shock. As I’m waiting for my appointment with genetics, would you be able to elaborate on any potential negative impacts this could bring to the baby while in my womb? I’ve been trying to stay off Dr. Google for obvious reasons. Any information you’d be able to provide would be very helpful and appreciated. Thank you for all you do.”

Dr. Fox’s Response

We did a full podcast on genetic carrier screening. I’m pretty sure I did it with Dr. Tamar Goldwaser. So, you can go back and check for the long answer, the long form answer on this. But the short answer is, in general, there’s nothing to worry about. When we do carrier screening, right…it’s a certain form of genetic screening, and there are many forms of genetic screening we do in pregnancy, which is why it sometimes gets confusing for people. But the carrier screening is the kind of genetic screening where we’re testing the parents to see if they carry certain genetic conditions. Cystic fibrosis is one of them. There are actually hundreds of them that we test for.

And since it’s a genetic test on the parents, it could be done prior to pregnancy. It could be done during pregnancy. The results are the same. Meaning, it’s not related to this particular baby inside of you. It’s related to your own genetic makeup. So, it can be tested at any time. And there’s a good argument to be made that, ideally, it should be tested before pregnancy. But that’s not always logistically possible.

But either way, what we’re testing for is to see if the parents carry certain genetic conditions. If you carry a genetic condition, the principle typically is that being a carrier has no impact on your health. Meaning, if you are a carrier of cystic fibrosis, you will not have cystic fibrosis as a condition. You will not have a disease. You will not have symptoms. You will not have anything. You just carry it. But since it’s what we call an autosomal recessive condition, if you go back to high school biology with the Punnett square, big A, little A, big A, little A, this is the kind of condition where you would need both of your genes to have a mutation in order to have the condition. So, how does that happen?

Let’s say the mother is a carrier. So, she is perfectly fine. She has no symptoms. She has nothing, but she carries it. And let’s say the father is a carrier. Similarly, he has no symptoms and has no condition. He’s perfectly fine. And they have a kid together. One out of four of those children will actually get the gene from each parent, right? One out of two of the mothers, one out of two from the father, 50% times 50% is 25%. One out of two times one out of two equals one out of four. So, 25% of the kids will actually have the condition cystic fibrosis.

And so, what we do in pregnancy or prior to pregnancy is we test the parents. And you can either test them at the same time or test the mother, then test the father, to see if they carry the same genetic mutations. And if they do, they would know that there’s a 25% chance of their child having the condition. And then if you are pregnant, you can choose to do, like, an amniocentesis or a CVS to check if the child did in fact get that condition. If you’re prior to pregnancy, you have the option of, let’s say, doing IVF and then selecting embryos that don’t have the condition and using those.

Okay. So, in your case, you found out that you’re a carrier of cystic fibrosis. What I would say is, number one, when you do expanded carrier screening on people in pregnancy, what you find is that the majority of people do carry some genetic condition. If you test for these hundreds of conditions, probably 70% plus of people do carry a genetic condition, and they would not know about it, nor would anyone in their family know about it, because all the people who have passed it down from generation to generation have passed it down as carriers. Meaning, none of them had the disease. And so, that’s not something that you would know in your family that one of your parents is probably a carrier for cystic fibrosis, and one of their parents is a carrier, and so forth.

So, what we do is we test, and we find if the…let’s say the mother is a carrier of cystic fibrosis. And then if the father’s not a carrier of cystic fibrosis, either he carries nothing, or he carries some other condition, then you’re good to go. Nothing to do. The chance of the baby having cystic fibrosis, it’s not zero, but it’s almost zero. Right? And then you’re done.

So, what typically happens is, at this point in pregnancy, you find out that you’re a carrier for cystic fibrosis. They’re going to have you meet with a genetic counselor, but what they’re essentially going to tell you is you’re fine. The father should get tested. Right? To check if he’s a carrier of cystic fibrosis. And if he’s not a carrier of cystic fibrosis, which is the likelihood, then you’re good to go. No issues.

If he is a carrier of cystic fibrosis, then what they’ll tell you is, okay, this child you’re carrying has a 25% chance of having the condition cystic fibrosis, and then you could decide what to do about that. Do you want to do an amniocentesis and find out before birth, or do you want to test after birth? But again, the likelihood of being in that situation where he’s also a carrier of cystic fibrosis is fortunately pretty low, again.

So, that was sort of, like, an overview of carrier screening as related to your question, but we did do a full podcast on this. So, you can definitely go back and check that one out if you want more information.

Learn More on the Healthful Woman Podcast

On the Healthful Woman’s podcast, we hope to increase patient education about a wide range of pregnancy topics and offer reassurance. We invite you to check out the full episode to hear other questions from our listeners.

Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

Carnegie Imaging for Women blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!