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

Michelle’s Question

I recently had a preterm birth, singleton, after being admitted at 25 weeks due to a dilated cervix with bulging membranes. It was too risky for a cerclage, so I ended up on modified bedrest in the antepartum wing. I had no signs prior. An anatomy scan at 22 weeks was great. No contractions prior. No infections via swab exam. Is a dilated cervix an element of cervical insufficiency? Could cervical insufficiency be avoided in future pregnancies? I understand bed rest is controversial, but would that be something to consider for future pregnancies in case of true cervical insufficiency, or is a cerclage the only proven solution?

Dr. Fox’s Answer

Thank you, Michelle, for your question. I am going to answer it. I’m also going to direct our listeners. If you want a full discussion on the topic of cerclage, I did a podcast with Dr. Rebarber in 2022, and we also did a Mailbag podcast in 2024 all about cerclages. It was Mailbag 14. Okay, for your question…

There are several questions in there. In terms of an overarching principle, you mentioned cervical insufficiency, formerly known as cervical incompetence. We don’t use that term anymore, number one, because it’s just kind of mean to say something’s incompetent. However, number two it is not entirely accurate. Incompetence implies all good or all bad, whereas insufficiency sort of implies not good enough for the job at hand, which is really what we’re talking about. And the idea behind cervical insufficiency is that conceptually there might be or there probably are people who, for whatever reason, their cervix, which is the bottom of the uterus, is not strong enough to hold in a pregnancy. And because of that, it shortens and dilates early, and these people are at high risk for either losing the pregnancy in the second trimester or an early preterm birth in the third trimester. So, conceptually, that’s what it is. And it makes a lot of sense conceptually.

The problem with the diagnosis is that it’s a little bit vague. For example, why would someone have this condition? Why would someone develop this, or why would someone be born with this, number one? Number two, how do we know if someone has this condition, right? Is there anything we can do when someone’s not pregnant to test them for this? The answer is no. Or, if someone has a short cervix or a dilated cervix, do we know that that’s the reason? And the answer is no. There are a lot of reasons someone can have a short or dilated cervix in the second or third trimester that have nothing to do with the strength of the cervix. For example, you mentioned things like contractions, right? If someone’s having contractions, their cervix will shorten and dilate. There’s nothing wrong with their cervix; they’re contracting. Or if someone has an infection or some sort of inflammation, it’ll cause their cervix to shorten and dilate. But again, there is no problem with the cervix itself. It’s a problem with the infection or inflammation.

So, part of the difficulty in sorting this out is that it is very hard to know for certain whether someone has this condition or not. And what ends up happening is that if we really believe someone has this condition, a sort of nebulous condition where the cervix is considered “weak,” we call it cervical insufficiency, then presumably the treatment would be something to strengthen the cervix. And the treatment we have for that currently is a cerclage, where we sew the cervix closed either prior to it happening, if they have a history of it, or maybe while it’s happening, if their cervix is short or dilated. And that’s the treatment. And so you would like to do a cerclage on people who have this condition, and you would like not to do a cerclage on people who don’t have this condition. And that’s where sort of all the difficulty lies in all the research, all the differences in opinions, and all sorts of clinical knowledge that has to come into this type of decision, is that it’s not easy. It’s complicated.

Okay. So, in terms of your situation, when someone’s cervix is dilated at 25 weeks like yours was, so you said that your doctors felt it was too risky for a cerclage. So, that is probably true, and it’s very unusual to place a cerclage after 24 weeks, at least in the United States. Very, very, very few people would do it. Reason number one is that a concern that it’s risky that during the procedure, your water could break or could cause you to go into labor, and then you would deliver. But number two, it’s also because we’re not sure that the reason is that your cervix is weak, because if there were really a problem with your cervix, we think it probably would have manifested earlier than 25 weeks. And so that’s sort of the reason why I would agree that it’s unusual to have a cerclage placed at 25 weeks.

Okay. So, to answer your question, does your dilated cervix mean you have cervical insufficiency? We don’t know. I would say if it presents for the first time at 25 weeks, that’s a little bit unusual, but not certain one way or another. If someone has it earlier in pregnancy, let’s say you have the same story but you were 16 or 17 or 18 weeks, it would make it more likely, but again, not definite. But it would make it more likely. Could it be avoided in future pregnancies, which is your next question? Well, you can’t avoid cervical insufficiency if you have it, right? If you have the diagnosis, you have it. But if we think someone has that condition, we avoid the problems, ideally, by doing it earlier in pregnancy. So, if I believe someone has cervical insufficiency for whatever reason, based on their history, based on prior pregnancies, this or that, typically we would do a cerclage in the next pregnancy, sometime before it would be an issue. So, whether that’s 12 weeks or 13 weeks or 14 weeks or somewhere in that range is when you would do it. Or if someone presents in this pregnancy for the first time, and let’s say their cervix is very short or dilated, and I think that they have cervical insufficiency, this is the first time it’s happening, I might place a cerclage at that time.

Again, the difficult part is deciding who does and who does not have cervical insufficiency versus another diagnosis. And since we don’t always know what we sometimes do in the next pregnancies, instead of placing the cerclage, just follow very closely with frequent ultrasounds to check the length of the cervix. And if it starts getting very short, very early, that would give more evidence that maybe this is cervical insufficiency, and we would place a cerclage. So, a typical sort of conclusion that doctors are going to reach about someone who had a dilated cervix at 25 weeks like you did is in the next pregnancy, either they would conclude we need to place a cerclage or they would conclude, “I’m not really sure. Let’s follow you very closely in the second trimester. And if your cervix remains nice and long, there really shouldn’t be a problem with your cervix. We won’t place a cerclage,” versus if it gets short in the second trimester, that plus your history of what happened to you before is enough evidence to say, “You probably have cervical insufficiency. Let’s place a cerclage.” So, that also answers whether a cerclage is the only proven solution. Well, it might be if you need it, but it might not be if you don’t need it.

In terms of bed rest, you are correct. It is very controversial whether it works or not. Certainly, in the setting of a short cervix and avoiding preterm delivery, what I would tell you is that the data is not good. There aren’t great studies evaluating this, but the data that we have suggests that bed rest is not helpful, meaning it does not keep people pregnant who have, whether it’s cervical insufficiency or a history of a preterm birth or a short cervix at this time. And so it’s not typically recommended. With that said, since the data isn’t perfect, we usually discuss activities to avoid and so on. And that has to be very individualized.

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!