“Mailbag #14: What does the Fox Say….about cerclages?” – with Dr. Nathan Fox

Welcome to today’s episode of “Healthful Woman,” a podcast designed to explore topics in women’s health at all stages of life. I’m your host, Dr. Nathan Fox, an OB-GYN and maternal-fetal medicine specialist practicing in New York City. At “Healthful Woman,” I speak with leaders in the field to help you learn more about women’s health, pregnancy, and wellness.

Hey, welcome to mailbag number 14, “What does the Fox say?” And today is a cerclage-centric mailbag podcast. We got three questions all related to cerclage, so I thought we would put them all together into one podcast to answer your cerclage questions.

All right. Our first question is from Christina. “After finding I was 1.5 centimeters dilated at my anatomy scan, and then a subsequent 22-week loss, I was diagnosed with cervical insufficiency. Your podcast on cerclages was immensely helpful as we met with MFM to determine how to move forward. Unfortunately, I went on to have 2 early miscarriages but then got pregnant again and made it to the point where I got a cerclage at 13 weeks. I went in to have a full-term pregnancy and delivered a healthy baby at 37 weeks and 4 days after getting my cerclage out at 35 weeks and 6 days.

Is there data to support that now that I’ve had a successful pregnancy with the cerclage, is a cerclage likely to work again in a future pregnancy? This pregnancy was so stressful, even though I was being seen bi-weekly by my OB and MFM. Having three pregnancy losses before having a healthy baby was a lot to deal with. And at 38 years old, I know I don’t have a lot of time left to try again without interventions like IVF. Thank you, Dr. Fox.”

All right, Christina, thank you for the question. I’m sorry you went through all that before you had your healthy baby. It is a lot. There’s a lot to unpack from your question. So first, in terms of cerclages, you, Christina, obviously know a lot more about this than some of our listeners might. But basically, as a background, a cerclage is sort of a stitch we place around the cervix in an attempt to keep in a pregnancy.

Now there’s a lot of reasons why we may or may not recommend that and do that. But if we think of them in sort of buckets of reasons, the first bucket is called a history-indicated cerclage, which is basically when we place a cerclage early in pregnancy before anything happens because of things that happened in someone’s past, whether prior pregnancies or something about their anatomy or whatever it is. But basically, it’s placed sort of… They used to be called something that’s prophylactic. And the idea is you’re placing it early in pregnancy to prevent something from happening later and you’re doing that because of something in the past. So that’s history-indicated.

The second reason is something that we call ultrasound-indicated, which is where in pregnancy someone doesn’t have a cerclage, but then an ultrasound, we see that there’s a short cervix. An ultrasound, and for whatever reason, we decide that a cerclage is the right treatment to sort of prevent pregnancy loss or preterm birth. And exactly how we decide which person with a short cervix does and does not need a cerclage is complex because it’s not everybody and it’s not nobody.

Okay. The third reason, which is what you were, in theory, a candidate for, was when someone has dilated, their cervix has dilated prior to 24 weeks, we call that either physical exam-indicated cerclage or we call it an exam-indicated cerclage. Sometimes people used to call these rescue cerclages or emergency cerclages, which definitely captures the feeling of the moment. It’s a pretty dire situation when your cervix is dilated in the second trimester and there’s a very high chance of pregnancy loss or very early preterm birth with no treatment. And then placing a cerclage at that time is a little more challenging surgically and the data on it are pretty good, but it’s hard to have very large studies with this. But basically, that’s a physical exam-indicated cerclage.

Okay. So going back to your question, you had a pregnancy loss where your cervix was dilated and then you lost the pregnancy, then you had, which could be a sign of a cervical problem, then you went on to have a few early miscarriages, which should not be related to the cervix, it’s sort of other reasons. And then your doctors decided that you were a good candidate to have a history-indicated cerclage in the next pregnancy. And that’s the one you had at 13 weeks.

So first about that decision, because it does play into your question about future pregnancies. Whenever we see someone who comes to us and says, “Hey, in my last pregnancy, my cervix was dilated in the second trimester and then I lost the pregnancy,” or, “I had a preterm birth,” or maybe, “I had a cerclage,” whatever it is, and they’re saying, “Do I need a cerclage in this next pregnancy history-indicated?” You would think, “Yes.” You would think, “Okay.” You know, last pregnancy, your cervix was dilated. Clearly, there was something wrong with your cervix. Clearly, you needed a cerclage.

But the problem is it doesn’t work out that cleanly, meaning there’s lots of reasons people could be dilated and lose a pregnancy in the second trimester or deliver early. One of the reasons is you have this condition called cervical insufficiency, sometimes called cervical incompetence where the cervix is, like, “weak” and needs a cerclage. But there’s lots of other reasons. Sometimes people have some form of, like, a subclinical infection or sometimes there’s a placental abruption or sometimes there’s an abnormality with the baby. And all of those can lead to a cervix opening or dilating and then losing the pregnancy, but there’s actually nothing wrong with the cervix.

So the decision to place a cerclage in the next pregnancy, a history-indicated, because of your first pregnancy is complicated. And we never know 100% if it’s the right thing to do or not. Now I don’t disagree at all that you had one placed. It’s certainly a very reasonable thing to do. The other option would be or would have been, I should say, instead of placing a cerclage at 13 weeks to have your cervix monitored serially, like every week or 2 in the second trimester, and if the cervix remains nice and long, not place a cerclage. Nothing wrong with your cervix. Or if the cervix gets short, place a cerclage because now it’s pretty clear there’s something going on with your cervix.

And it’s interesting if you look at people like you who had a pregnancy loss with a dilated cervix and then in the next pregnancy, if you don’t place a cerclage, it ends up being ballpark 50/50, whether your cervix would have gotten short and you would have needed a cerclage or whether it actually would have been fine the whole time and you would not have needed a cerclage. And that just again tells us how complicated this process is and how we really don’t ever know 100% what the issue was.

So the decision was made in your pregnancy to have a cerclage at 13 weeks. Again, I don’t disagree with that decision. I’m just saying it could have gone either way with what to do. The cerclage was “successful” because you got to 37 weeks and you had a healthy full-term delivery.

So now you’re asking me, “What about the next pregnancy?” And we’re sort of left with the same question, right? We don’t know 100% if you have this condition, cervical insufficiency, or whether you don’t have it. Certainly, you could. Your story would definitely fit the pattern of someone who does, right? In one pregnancy, your cervix is dilated and you lose the pregnancy, and then in another pregnancy, you have a cerclage placed and you don’t lose the pregnancy. So that certainly would be consistent with someone with cervical insufficiency.

But your story could also be consistent with someone who had a different condition in the first pregnancy. Maybe you had what we call a subclinical infection where there was, for whatever reason, some sort of infection and inflammation inside the uterus, and that’s what caused your cervix to dilate and lose the pregnancy. And then the next pregnancy, even if you didn’t have a cerclage, you would have went to 37 weeks. Now nobody knows, right? You can’t go back in time and change what you did and see. You know, it just doesn’t work like that.

And so I would say at this point, it’s sort of the same decision that’s available to you. You can either say, “You know what, there’s a good chance I have cervical insufficiency. I went through a horrible pregnancy loss, then I had a cerclage and it wasn’t such a big deal, so to speak, and I went full-term and everything went well.” Why rock the boat? Just place it again in the next pregnancy. The risk of the procedure is pretty low and you’re probably going to do well. And why not? Worst case scenario, you’re having a cerclage that is “unnecessary.” Again, there might be some downside, but probably not a ton.

On the other hand, you might say, “You know what, I really don’t want a cerclage if I don’t need one. I don’t want surgery if I don’t need it.” Or maybe, “I’m thinking of having five more kids and I don’t want to have a cerclage with five more pregnancies. I really want to know for sure whether I have this issue with my cervix or not.” And so the alternative is not to place a cerclage and to do again ultrasounds every week or 2 starting around 16 weeks and see what happens with your cervix. And if it gets short, you sort of know, okay, it’s probably the cervix. Have a cerclage then. And if it doesn’t get short and it stays nice and long to know that, you know what, it probably wasn’t an issue with my cervix in the first place.

And I have to tell you, this is something that comes up frequently when I see people who have a history either of a loss or a history of a loss than a cerclage, and we go through this that, again, I can take my best guess what I think it is, but we have to have some level of humility that we don’t always know. And we see people who have a story like yours and had a cerclage and they decide not to have a cerclage the next time. Again, some of them end up needing a cerclage and some of them end up not needing a cerclage, like, wow, she never had a cervical problem. And obviously, we have people who choose to just have the cerclage, which is again quite reasonable. And then we don’t really know for certain what it was. I mean, ultimately, if you have healthy babies, it doesn’t really matter if you know.

And so I would say the short answer to your question, I just gave you a long one, is that it’s not that you definitely need a cerclage. We still don’t know. It probably would work out well if you got one. And if you didn’t get one and monitored very closely, I would tell you it’s ballpark 50/50 whether you would ultimately need one or not based on your cervix getting short.

As an aside, thank you for what you said about the podcast and how it was helpful. It is literally the single reason that we do the podcast is so that people like you going through these situations do have a place to go for good information that’s hopefully accurate and reasonable and understandable. Okay, great question, Christina.

All right. Question number two about cerclage is from Melissa. “Hi, Dr. Fox and team. I am so glad I found this podcast in the midst of my di/di twin pregnancy. The information I’ve already gained is appreciative and insightful for sure. So thank you. My question is this. I’m 25 weeks pregnant with the twins and I just found out my cervix is only 1.5 centimeters, I guess, long. Earlier, it was 5 centimeters long, then 2.5, and now 1.5. Needless to say, this is a scary bit of information.

After my last scan on Friday, my MFM doctor sent me over to the labor floor for precautionary steroid shots for baby’s lung development and to monitor for any kind of contractions. Luckily, no contractions. I asked about progesterone and the on-duty doctor didn’t seem like he was on board with it actually helping and neither was the nurse. So for now, it’s a terrible wait-and-see situation until my next scan. In your experience, what is there to do in a situation like this? I know there’s no predicting the future and what my body and cervix will do, but I just want to keep these babies in as long as possible. Thank you for taking the time to read this. And if there’s any articles or previous podcasts I can refer to for this as well, I will definitely give a read or listen. Thank you, Melissa.”

All right, Melissa, thank you for the question. Short cervix in twins. So twin pregnancies, all twin pregnancies have an increased risk of preterm birth, preterm delivery, right? So if you’re carrying 1 baby, on average, you’re going to deliver 39 to 40 weeks, which is the week of your due date. If you’re carrying 2 babies, you’re carrying twins, on average, you’re going to deliver 35 to 36 weeks, which is 1 month earlier. And this seems to be true across the board.

Now there are things we can do to predict who a twins is going to deliver earlier. So one of them is if we did a transvaginal ultrasound to measure the length of the cervix. The shorter the cervix, the higher the risk of preterm birth. And on the flip side, the longer the cervix, the lower the risk of preterm birth. Now, checking the cervical length is a screening test, meaning it does not definitively say who’s going to deliver early and who’s not going to deliver early. It’s all just about changing your odds and your risk.

And so in our practice, we typically do cervical length screening routinely on twins. We do it approximately every couple of weeks, starting at 16 weeks. This practice varies greatly in the U.S. and around the world. Some people do it like we do it, every couple of weeks. Some people do it once or twice in the second trimester. Some people don’t do it at all.

And the controversy about whether to do it or not do it is not really a disagreement about the information it provides, meaning all the data says the same thing, that as your cervix gets shorter, the risk of preterm birth is higher. Everyone agrees on that. It’s not like there’s a dispute over that fact.

The reason people disagree is, okay, what are you going to do about it? Right? So if I find someone with a short cervix, is there anything I can do that’s going to actually improve outcomes and have you deliver later versus earlier? And that’s where there’s a lot of disagreement amongst people. And so if someone believed that there was nothing to do about someone with a short cervix and twins, you could reasonably conclude that maybe I shouldn’t bother checking. Why have someone undergo all these ultrasounds and maybe add some stress to their life and whatnot if there’s nothing I can do about it?

So the reason we do it in our practice is, number one, there is sometimes you can do something about it. And that’s what we’ll talk about to answer your question. But even if there weren’t, meaning even if I were to accept the premise that there’s nothing you can do to change when someone’s going to deliver, we’ve always maintained that there is value in knowing who’s at the highest risk for delivery early versus not knowing.

And one of those values is you can sometimes prepare for a preterm birth, doing things like giving steroids, which is what you, Melissa, got when you went to the labor floor. That’s if you deliver early, if the babies were exposed to steroids, meaning you get them, babies are exposed to them, they tend to do better in the NICU. There’s other things we can do, sometimes it’s magnesium, sometimes antibiotics, and depends on the circumstances. So that’s one kind of preparation, like, practical preparation for the babies.

But also just for people carrying twins, frequently they want to know, like, how high risk am I? Should I go on that 24-week baby moon to Anguilla or should I not go? And that’s its own conversation. But if someone’s cervix is very, very long, it’s a much lower risk proposition than if your cervix is very, very short before your trip. And so that’s something like that. Or are these symptoms I’m feeling sort of normal or they’re indicative of a bigger problem? So, you know, there’s definitely some reason in our opinion why it might be valuable to know the information, even if it won’t affect when you’re going to deliver. So we do that. So we do check the cervix routinely.

Now your question, Melissa, is related to, all right, you are someone with twins who has found to have a short cervix. What can we do about it? So some of that depends on when it’s found and some of that depends on how short it is. When you’re under 24 weeks, which is not your situation, but let’s say someone was under 24 weeks, there is reasonable data that giving vaginal progesterone to someone with twins and a short cervix is helpful. Not all the data is consistent, but it does seem to point in that direction.

And so based on how short the cervix is, if you’re under 24 weeks, we do tend to prescribe vaginal progesterone in the hopes that it will prolong pregnancy somewhat. And there definitely are data to support that, not as robust as the data to support that for a singleton pregnancy, but there are data for twins.

Whether a cerclage is helpful is a really controversial topic when we’re talking about twins with a short cervix. There’s pretty good data that placing a cerclage in everybody with twins is not helpful, meaning most people with twins are not going to benefit with a cerclage. So there was a thought many years ago that maybe everybody with twins should get a cerclage and that the data points against that.

If you look at the… So that’s a history-indicated cerclage with the history being I have twins. If you look at people with a dilated cervix and an exam-indicated cerclage, the data isn’t great because it’s not that common, but the data seems to point that a cerclage is probably helpful in someone with twins and a dilated cervix.

With twins in a short cervix, the data is mixed, the data is sparse, meaning there’s not a ton of data on this, and it’s very controversial. It has gone from people recommending a cerclage in all twins with a short cervix, then the pendulum swung and it was nobody with twins and a short cervix should get a cerclage. And I think where we are nowadays is there are probably some people with twins with a short cervix who would benefit from a cerclage, but it’s very hard for us to know for sure who those are.

One of the ways to sort of differentiate who might benefit from a cerclage and who might not with twins is, how short is it? And we published a paper several years ago where we looked at twins with a short cervix who got a cerclage placed. This was not just our patients, but sort of multi-centered. It was retrospective, so it’s limited. But basically, in that study, overall, twins with a short cervix did not benefit from a cerclage, but it did seem to indicate that twins with a very short cervix under 15 millimeters did seem to benefit from a cerclage. Now again, that study doesn’t prove that placing a cerclage in someone with twins in a cervix under 15 millimeters is helpful, but it sort of pointed that maybe, right? And more research needs to be done.

So I would say for someone who has twins and a short cervix under 24 weeks, typically a cerclage is not placed, but there might be case-by-case scenarios where we would recommend it or talk about it or say it’s a reasonable option.

Now you were 24-plus weeks, so you were 25 weeks when the cervix was short. In the U.S., there’s very few people who would recommend a cerclage and twins after 24 weeks because there’s not a lot of evidence that it’s helpful and it could potentially cause some issues.

Whether vaginal progesterone is helpful or not is also questionable. Most of the studies looking at vaginal progesterone in twins, it was under 24 weeks. I don’t have a problem with vaginal progesterone after 24 weeks, like at 25 or 26 weeks, because I don’t think it’s harmful. And maybe it’s helpful, but it’s hard to know for sure.

And so there aren’t a ton of interventions that we have that we know of that can lengthen pregnancy for you or reduce that risk of delivering early. But again, it sounds like your doctors were focusing on sort of preparing in case you delivered early with things like the steroids.

What’s interesting though is just because your cervix is 1.5 with twins does not mean you are going to deliver very early. There are other factors involved. So for example, like, in our practice, we do a test frequently called a fetal fibronectin test, which if it were negative for you, your chance of delivering early is much, much lower. Whereas if it were positive for you, the chance is higher. Similarly, are you having contractions? Are you not having contractions? Similarly, what’s going to be over the next two weeks?

And a lot of twins will have a short cervix, probably about a third of them. And so it’s a very common phenomenon, but not all of them are going to deliver early or very early. If you want, you can go to our website for my practice. It’s mfmnyc.com\win. And we actually have there a twin preterm birth calculator where you can plug in your gestational age, your cervical length, and the results of your fetal fibronectin positive, negative, or I didn’t do one. And it’ll actually predict when you’re going to deliver and the likelihood of delivery before each gestational age sort of window. And so that might be helpful for you or for others in a similar predicament, just sort of knowing how bad does it seem to be.

And again, if you look at that calculator and you play around with it, the shorter the cervix is, the higher the risk, but also that fetal fibronectin test being positive or negative will change your risk significantly. Again, not everyone does those tests routinely, the cervical length or the fetal fibronectin but that is data that you could possibly get to help predict what’s going to happen in the future. All right, Melissa, thank you for the question. Really good one.

Next question is from Taylor. “Hi, Dr. Fox. My first pregnancy ended at 18 weeks due to an incompetent cervix. I had no signs of preterm labor. My water just broke and the next thing I knew, the pregnancy was over. It’s been 5 months and I’m pregnant again, just about to be 11 weeks. I’m debating between getting a preventative cerclage at 13 weeks or getting closely monitored by my doctor.

My question to you is, my doctor’s offering to see me every 2 weeks to check my cervix between 16 to 24 weeks. Do you think monitoring at two-week intervals is enough? Ideally, I’d like to be seen twice a week, but I’m trying to be reasonable and ask for an appointment once a week. What do you think is a reasonable amount of monitoring to ensure we catch any shortening before it gets too dangerous?”

Taylor, that is an amazing question. Thank you for the question. I’m sorry, obviously, that you had the pregnancy loss. That’s horrible, and I wish you all the best in this pregnancy. So again, as I was saying with the first question when I was giving the background to Christina’s question, it’s really not certain that the pregnancy loss you had at 18 weeks was due to incompetent cervix or cervical insufficiency. It certainly is suspicious for that, right, because that would be something that could happen if you had a cervical problem.

But again, it’s really hard to know. Maybe the water broke for some other reason, like an infection or something like that. And once the water breaks, then you would go into labor and lose the pregnancy, but it doesn’t mean that there’s something necessarily wrong, so to speak, with the cervix, right? Because the only reason a cerclage, only reason that makes sense that a cerclage would actually help is if the problem is in the strength or the integrity, so to speak, of the cervix, right? If the problem is contractions or the problem is bleeding or the problem is infection, a cerclage wouldn’t really help that. It would really only help because you’re just sewing the cervix closed if the cervix itself is weak.

And like I said before, you know, ballpark, your chance that this was due to the cervix is about 50/50. So if you chose to do monitoring as opposed to the cerclage, there’s about a 50% chance that at some point your cervix would become short and you would get a cerclage and about a 50% chance that your cervix would never become short and you wouldn’t need a cerclage. And which strategy to go, different people choose differently.

Now, the there’s upsides and downsides to both. And this is where I’ll get to your question. So the upside to placing the cerclage is you don’t have to think about it. You don’t have to sort of worry about it. You don’t have to, like, keep coming to the doctor worrying today the day my cervix is going to be short and I’m going to have an emergency cerclage, so to speak.

But also, if I chose the monitoring, there’s always that chance that between visit number one and visit number two or visit number two and visit number three, what if between that time I lose the pregnancy? Right? What if my cervix is normal on Monday and then my next appointment is two weeks later, but between that appointments, my cervix gets short, dilated, and I lose the pregnancy? Whereas if I had a cerclage, I wouldn’t have.

And that’s a legitimate concern. It doesn’t usually work like that. Usually, if it’s cervical insufficiency or cervical incompetence, usually there’s changes we’re going to see in the cervix that precedes you losing the pregnancy. And so typically we would see a short cervix before that happens.

But how frequently should one be seen in order to not miss a pregnancy loss is sadly unknown. And so one option like your doctors offered was every two weeks. Another option like you were suggesting as a middle ground is every week. I don’t know a lot of people who do twice a week.

And so in our practice, we usually do every two weeks or every one week based on how concerned we are over the situation. So if it’s someone who there’s a really good chance we think it’s more than 50% that there’s a problem with the cervix or their story is such that everything was normal last pregnancy and then within a week or two they’re basically losing their pregnancy, we’re definitely going to err on the side of doing it weekly.

Whereas if it’s someone who maybe it’s a little bit more borderline or a little bit less complicated or they just don’t want to come every week, then we’ll do it every two weeks. And there isn’t a perfect answer. I would tell you that for you having an 18-week loss, I would definitely think that it’s reasonable to do it weekly. I certainly have no problem with that.

And it’s probably what I would have recommended only because if you do it every 2 weeks, you’re basically going to have 1 scan when you’re about 16 weeks and then the next one’s going to be around the time you lost the pregnancy. So at least me personally, I’d probably want to see you every week, you know, starting at 15 or 16 weeks through at least, I don’t know, 20 weeks, maybe even later, and then maybe go to every 2 weeks.

So I think your plan is reasonable, but it’s very hard to say with certainty what is the right plan or what is the necessary plan. I would say in practice, you know, I’ve been doing this a long time. I can’t remember. I don’t think I can remember any time where someone was doing weekly and it was sort of normal one week and then before the next appointment, they lost the pregnancy due to a cervical problem.

Other problems can happen over the course of a week. You could suddenly start bleeding or this or that. But in terms of what we’re thinking the process could be, weekly tends to be sufficient to do it. And for most people, every other week is also sufficient. But certainly, I would think weekly. So if you land on weekly, I would say that’s probably quite reasonable and should help.

All right. I’m glad we got to do all three of these mailbag questions together to put them all for cerclage for anyone who’s in this sort of camp thinking about cerclage, had a cerclage, doesn’t know if they need a cerclage. As some of the listeners mentioned, we do have other podcasts on cerclage from before, so you can check those out. If you’re carrying twins, you can check out our preterm birth calculator that I mentioned before, and good luck to all of you. Thank you, Christina, Melissa, and Taylor for your awesome questions. Have a great week, everyone.

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