Episode 261 Dr. Nathan Fox + Scar Thickness, Uterine Rupture, Due Dates & More

Dr. Nathan Fox is a practicing OB/GYN and Maternal Fetal Medicine provider in New York City. Two of his children were also VBAC babies! He joins Meagan on the podcast today where they discuss topics in depth to help listeners make more informed decisions about their VBACs. 

Topics today include where to find evidence-based information, how to interpret it, the risks of uterine rupture, VBAC and COVID-19, induction, scar thickness, due dates, and third-trimester ultrasounds. 

Additional Links

Healthful Woman Website

MFM, High-Risk Pregnancy New York City Website

Needed Website

How to VBAC: The Ultimate Prep Course for Parents

Full Transcript under Episode Details 

Meagan: Hello, hello. You guys, it’s November. How are we at the end of 2023? It is crazy how fast this year has gone. We have a special guest today. It’s Dr. Nathan S. Fox. He is so amazing to come on today to talk to us about a couple of topics that I don’t know if we’ve actually ever talked about on the podcast. 

We’re going to be talking about scar thickness. We’re going to talk about third-trimester ultrasounds. We’re going to be talking a little bit about COVID and is it really best to induce at 39 weeks? We’ve had COVID. What does it mean with our placenta? We know we’ve been hearing it out there where our placentas are not doing well. So you guys, get ready. Buckle up. It’s going to be great. 

I want to tell you a little bit about Nathan Fox first. He is a board-certified OB/GYN and he is also certified in MFM which is Maternal Fetal Medicine. In his clinic, he sees a lot of higher risk and unique situations. He did his residency at Mount Sinai. He has an amazing podcast that really dials in on helping people know the evidence and then also understanding the evidence in English because if you are like me, you’ll know that it is kind of hard to break down some of these studies sometimes and it’s hard to understand what the evidence is even saying and then how to apply it. 

He has this podcast and it is Healthful Woman. We are going to make sure that it is linked. You guys, he has so many incredible guests on there talking about a wide range of things. It’s not VBAC-specific, but it definitely has a wide range of topics and things that you’re probably going to love. Definitely check that out. We’ll have it in the show notes. Dr. Fox, seriously, we are so grateful for you today. We can’t wait to have you on. We’ll be right back. 

Dr. Nathan Fox

Meagan: All right, I need to pull up those questions really fast. There are a lot. Literally, we do not have to get to all of them. 

Dr. Fox: I’ll come back if you want. Don’t worry about it. 

Meagan: Yeah, we’ll have to do a part two. You are so sweet to take the time out of your busy life, I’m sure. 

Dr. Fox: We are mission-aligned as they say in the fancy world. It’s about getting good education, and good information out to people so they don’t have to hear crazy stuff on the World Wide Web and get terrified. 

Meagan: Right. That’s why we started this podcast even just to share stories of people who are having VBACs so people can hear and learn through those VBACs and also know it is an option and it is possible. 

I have a question. You said before we started recording that you have two VBAC babies. 

Dr. Fox: Yeah. 

Meagan: How was that journey as an OB and MFM? Was your wife getting information that you were like, “Wait, that’s not true,” or were you like, “Actually, we need to think about this”? How was that journey as someone in the field?

Dr. Fox: Full disclosure, I was getting into the field. I have four kids. My first two are twins and they were born when I was a medical student so I knew very little. I guess more than nothing, but closer to nothing than where I am now. They were born by C-section. Both of them were breech. Thank God, both of them did great. All was well. 

With the next one, my wife was pregnant when I was a second to third-year resident in OB/GYN. For most of her pregnancy, I was a second-year, then she was born a month after I became– not even. She was born July 17th so 16 days after starting my third year. 

Meagan: Right after, yeah. 

Dr. Fox: I knew a little bit more then. That was our first VBAC. Then my fourth was born when I was an MFM fellow. I like to say that I had kids in all of my points in training. Honestly, we didn’t think much about VBAC in terms of being this grand decision and conversation. I would say mostly because the OB my wife was seeing was on board with it and didn’t make it into a big deal and she was delivering at a hospital at Mount Sinai where I trained and where I now practice where VBAC is commonly done. There was a conversation about it. It wasn’t like we were blind to it, but it was part of the normal culture in that hospital on the labor floor so we didn’t think much about it. 

My wife said, “Why would I want a repeat C-section if I can try and do it vaginally?” It worked out fine, thank God for both of them. The third was also actually a forceps. We’re like a textbook of obstetrics, my wife. But yeah. It wasn’t dramatic. Let’s put it that way, the VBAC process.

Meagan: Wow. Yeah. I love hearing about it that it was just a thing. It didn’t have to be a big deal. She was just going in and wanted to have a baby. She didn’t want to have a C-section.

Dr. Fox: Yeah, again, I think it is something that should be discussed. People should understand and not even everyone understands that it is a thing meaning people don’t even realize why you wouldn’t. 

Meagan: Why you would not, yeah. 

Dr. Fox: There is risk, but ultimately, if it is an option, the risk of a VBAC– again, in the right person– is not markedly higher than the risk of a C-section. So it’s a conversation. Which risk would you prefer or which risk would you least prefer? So that conversation was very straightforward. “Would you want a repeat C-section? Would you want a VBAC?” She was like, “I want a VBAC.” Fine, so that was done. It wasn’t like she had to meet with an attorney to go over everything and sign a waiver or anything like that which sometimes happens. 

Meagan: Yeah. I love hearing that. Well, I am so excited that you are here with us today. I know that we have so many questions to dive into. They’re kind of all over the place. With the first one, I think a lot of our community members– we have a Facebook community, a forum, and one of the most common posts in there is looking for a provider that is supportive because they were with a provider and then they found out that the provider that was seemingly supportive is not supportive anymore. 

It all seems to focus around things with evidence-based information and they’re getting all of the different things. One of the questions is why is it so hard to find evidence-based information on VBAC, VBAMC, and uterine rupture– because we have some providers that are saying you have a 60% chance of uterine rupture and then some saying you have a 0.4-1% chance. Those are very dramatic numbers. The range of answers is just so wide. I’m just wondering why do you think it’s so hard and where can we find this information. Where would you suggest our listeners go? Let’s talk about your podcast being one of those places. It’s not just VBAC-specific. Your podcast isn’t VBAC-specific but it’s very, very good at a whole, wide range. 

But yeah, can we talk about where to find evidence-based information about birth in general but especially about VBAC?

 

Dr. Fox: I mean, yeah. That’s really the million-dollar question. I think that both the problem and solution are essentially that we have access to all of the information that’s ever been available ever. There was a great Simpson’s thing where Homer Simpson said, “Beer. The cause of and the solution to all of my problems.” 

Information is the same way. On the one hand, it is unbelievable how much information we have access to and that’s a great thing. It’s not hidden. It’s not only amongst the elite that have the information. Everyone can have the same information so that’s the good part. The bad part is it’s very difficult to sift through all of that information and find a) what’s correct or b) what’s applicable to me. 

So for example, let’s say I’m someone who has a prior C-section and I have a friend who is also someone who has a prior C-section, but one of us has a prior low transverse C-section and one of us has a prior classical C-section. How do we know that we have different percent risks? It’s a high level in a certain sense. So sometimes the websites or the podcasts or whatever will spell it out for you and explain it very clearly, but other times, you just get a list like, “Okay, the risk is this, this, this, and this.” You can’t really apply it appropriately. 

One of the things we try to do in our podcasts is to be much more user-friendly and to really explain it and what would apply to you, what wouldn’t in certain situations, and what questions to ask, but I would say for people trying to find information, usually it’s a shotgun approach. You Google something and find a website then find a list. 

You have to be very cautious and make sure that this applies to me and my unique circumstances. Hopefully, you have a doctor or a midwife who can help you with that. You might not. It’s possible that you may not. The other part is sometimes, it’s hard to interpret data. Understanding medical literature is a science. It’s something that we train to do. We practice it. 

I do a weekly journal club with the OB/GYN residents. This is the top of the food chain. These are the smartest of the smart. They got into a great undergraduate. They got into medical school. They got into residency. These are really, really smart people. It’s not always intuitive when you read a study or several studies on how to interpret it and apply what is and isn’t applicable. It’s very difficult stuff. I would say don’t be dismayed if you are not understanding the information out there or seeing such variation because you are in the same boat as all of us. It’s hard. It’s hard to get the right information out there. 

Meagan: It is. Yeah. Even when I’m reading through studies or things, it’s even hard for me to just understand what it’s saying and what the relevance is of it and all of it, so yeah. It’s really hard. I think what you said, “Don’t be dismayed,” it can be really frustrating when we’re out there and we’re like, “Okay, I have a special scar or not a normal low, transverse incision. What does this mean for me? What does this mean for my future? What does this mean for right now?” It’s really hard.

I think you nailed it where one friend can have this and one friend can have this. You can both have similarities in your risks, but they also don’t apply because there are other things going on in addition. 

Dr. Fox: There are facts like what is the truth? What is the true fact? There are always some brackets around those numbers because different studies will find different things. Let’s say one study finds 1% and one study finds 4%. Is it 1? Is it 4? Is it the average of the two? Is it a range from 1-4? There are some nuances in that. 

But then there is also trying to sift through the interpretation of the fact. A lot of that is why sometimes you’ll see different doctors feel differently about something. For example, let’s say the risk of uterine rupture is– let’s just do very rounded, broad numbers. Don’t hold me to it. Let’s say the risk of uterine rupture is 1% and if you’ve had two C-sections, let’s say it’s 2%. Let’s say those are the true numbers and you can argue about those. Those are the numbers. 

I could describe those very differently. I could say to somebody, “All right, you’ve had one C-section. Your risk of rupture is 1%. You’ve had two. It’s a little bit higher. You need to know that it’s now 2%. Maybe your chance of a successful VBAC is a little bit lower.” Okay. I could say it that way or I could say, “Whoa, your risk of uterine rupture where the baby could die is doubled.” Right? 

Meagan: Yeah. That just gave me the chills. 

Dr. Fox: That’s the same number. I’ve said the same thing in two very different ways. One person hears it and says, “It doesn’t sound like a big deal. My doctor said it’s fine.” Another person said, “My doctor said that my baby is going to die.”

Meagan: Doubled and die, yeah. 

Dr. Fox: It’s understandable because the doctors and midwives, people who are pregnant are all humans. Humans are complicated beings. We have emotions. We have fears. We have experiences. We have anxieties. We have all of these things that come into our heads and it colors how we view risk and how we describe it to other people. 

So I would say that another lesson is when you are getting information, try to differentiate the numbers and the hard facts from the interpretation of the number or the feeling about the number. That’s why you always have to be very cautious when someone says increased, higher, or doubled. That’s a relative risk, right? The risk of something is increased. Well, by how much? Is it increased a lot or a little? If the number was very, very low, is it still very, very low but a little bit higher?

I always give people an example. If I walk across the street, there’s a certain chance that someone moving a piano is going to fall on my head. If I look up every time I cross the street, I’m going to lower that risk but it doesn’t matter. The risk is so low to begin with that it doesn’t have any practical application to me. It’s sort of the same thing. You can talk about something increasing or decreasing your risk, but if the risk is still very, very low anyway, it may not matter to the person practically. 

Trying to get that from a provider is sometimes difficult because they may not know themselves the actual numbers. They may just know increased or doubled or this. They may be so colored by it that they have a hard time talking about it just as numbers or vice versa. They might just give you hard numbers and you want to know how they feel about it and they’re not giving it to you. It is hard, but that’s one thing to try to think about or differentiate. 

Meagan: I love that. I love that. 

Okay, this can be a very political topic. 

Dr. Fox: Oh, all right. You’re not going to mention Trump. Are we going to talk about Trump?

Meagan: We are not talking about Trump. 

Dr. Fox: Everyone in New York talks about Trump. We like him. We hate him. We hate him. We like him. It’s all we talk about. 

Meagan: I bet. I bet in New York, it’s really hot. Maybe in New York, this is even a hot topic but we’re going to talk a little bit about COVID-19. 

Dr. Fox: Oh okay. 

Meagan: We have a lot of moms who had babies during COVID-19. It was a really hard time for everyone involved. Giving birth as a provider, as a nurse, and everybody in life. This whole world of ours. 

Dr. Fox: It was unpleasant. 

Meagan: It was and that’s putting it nicely, I think, in a lot of ways. 

Dr. Fox: I still have scars on my face from wearing my N-95 for six straight months. 

Meagan: I bet. I bet. It is. It was a very traumatic time. 

Dr. Fox: Yeah. 

Meagan: We’re interested to see if you felt like COVID-19 had an impact on the C-section rate and if you saw more inductions happening and things like that. But right now, we have a lot of our moms being told even today, that if they had COVID-19 during their pregnancy from the time of conception to the end, they have to give birth by 39 weeks. 

Dr. Fox: By 39 weeks or after? 

Meagan: By 39 weeks. What they’re being told is that their placentas will just crap out. They’re just done. So it can be really hard in the VBAC community when they’re being told this and then we may have a provider who doesn’t want to induce. 

Dr. Fox: Yeah, yeah. For sure. 

Meagan: We have providers all over the world who are not comfortable inducing. We have VBAC moms who are like, “I want to have a VBAC. I had COVID when I was 20 weeks. I’m fine. All is well, but now I have to have a baby at 39 weeks. Here I am and my body’s not doing it.” 

Dr. Fox: Yeah. There is a lot there to unpack. No, it’s okay. You’re throwing fastballs at me. I like it. You’re throwing heat. I’m ready. I knew it was coming. 

Whether COVID increases the risk of things like the placenta crapping out so to speak is itself a controversial question. The data on that is mixed. It seems that there are some people who COVID has a negative impact on their placenta that manifests as the baby is not growing well. It can manifest as the baby getting preeclampsia. The worst-case scenario is that it can manifest as a stillbirth. However, you wouldn’t expect the stillbirth to come out of nowhere. You would expect there to be multiple things leading up to it like the baby not growing well, the blood pressure going up, the fluid dropping, and a lot of things instead of a sudden stillbirth. 

Meagan: Right, warning signs. 

Dr. Fox: Now, that is different from someone with COVID who is in the midst of a very severe COVID infection. That is very dangerous to the mother and potentially the baby but we’re talking about someone who got COVID and recovered or someone who just found out they had COVID and are fine, that type of thing. A) the data is questionable and B) what to do about it is also questionable. 

Let’s say you’re over the age of 35. You also have a slightly increased risk of all of those things if you had IVF. There is a whole list of things that put you at increased risk of your placenta crapping out so to speak and what to do about it is also more of a philosophical question than a hard-data question. Whether someone has to be delivered– I wouldn’t say before but usually at 39 weeks– because they had COVID, I’m not doing that personally in my practice. We do follow up and do an ultrasound to make sure the baby is growing well, but if someone had COVID at 20 weeks and is otherwise doing well later in pregnancy, we don’t say they need to be induced at a certain point. That’s not something I’m doing. 

I’m not aware of anybody in professional societies like ACOG, American College of OB/GYN, or the Society for Maternal Medicine who actually recommended that or advocated that, but again, some individual doctors are very uncomfortable with any risk. I think the other part of this that is really coloring a lot of these discussions nowadays is there was a study called the ARRIVE trial that got published a few years ago. It’s a very, very good study. The study was essentially designed to test if inducing everybody– these are low-risk, first-time pregnant moms. The lowest, lowest risk whether inducing everybody at 39 weeks improved outcomes or worsened outcomes. The outcome they really looked at was the death of the baby. It did not have any impact on that in either direction. 

What they also learned was that the rate of C-sections did not go up by getting induced. That was the biggest, I don’t want to say surprised because medically, we actually thought that would happen, but in the community, that was a surprise because everyone was always told that if you get induced, you have an increased risk of C-section so the study did not show that. It showed a slightly lower risk of getting higher blood pressure which makes sense because the longer you are pregnant, the more it goes. 

The way I look at that study is if I want to induce someone or if a patient wants to be induced at 39 weeks, there’s an upside. There’s a downside, but the downside does not include an increased risk of C-section. The downside could be longer labor. It takes more time. It’s not as pleasant. Okay, fine. That’s how I look at the study. 

Some people took the study and interpreted it to say, “Since there’s no risk of C-section, you should induce everyone at 39 weeks. That’s the optimal thing to do.” 

Meagan: And it’s happening a lot.

Dr. Fox: Yes. There are definitely people interpreting it. I don’t think it’s an unreasonable interpretation because you could say, “Listen, if I’m delivering you, there’s no chance for a stillbirth in the next two weeks,” I get it. But I don’t think it’s the only interpretation and it’s also a very impractical interpretation because if you induce someone, the amount of time they are in the labor room is on average 18 hours. 12-24 hours they are in a labor room. A common labor on their own, the average is let’s say 6-12 hours or something like that. So if you induce everyone, you need twice as many labor rooms. I don’t think every hospital in the country plans to double their labor floor so now, you just can’t do it practically. 

This is a very, very long answer to your question. I think what’s happened is that you have a new risk factor which is COVID which is very prevalent. Everybody got COVID basically at some point and you have a new fact that inducing at 39 weeks does not seem to increase the risk of C-section so there are some people concluding, “Well, I have a risk factor, and inducing at 39 weeks isn’t ‘bad’ so I’m going to affirmatively recommend it on everybody.” That’s tough. I don’t usually recommend it. If they want it, I think it’s an option but I think that that’s again, hard to know when you sign up with somebody who has provided prenatal care what their philosophy is. 

These are questions you probably want to ask very, very early on in prenatal care. Again, the things that really matter. So for example, if it very much matters to you not to have an episiotomy, you should ask very early, “Do you perform routine episiotomies?” Most OBs these days will say no, but if your OB says, “Yeah. I do them on everybody,” and you don’t want that, get the hell out. Switch. 

Meagan: Yeah. It’s probably not your provider. 

Dr. Fox: Yeah, and again, if it doesn’t matter to you, then don’t ask that question. Or for example, let’s talk specifically about VBAC. Very early on, just ask, “What are your thoughts on VBAC?” They’re not going to lie to you. They’re going to tell you. If they don’t tell you, you’re going to be able to tell right away. If they say, “VBAC is awesome. I love it. I love it when I can help someone with a VBAC. It’s so satisfying. It’s rewarding. There are some risks and we can talk about that. I think it’s great.” Versus they could tell you, “I don’t do them.” Or they say, “Yeah, I’m okay with that but I don’t know.” They’re telling you. They’re telling you that it’s okay, but they’re clearly not a fan of it. 

Meagan: They’re not gungho about it. 

Dr. Fox: Or the question is if they’re gung-ho, you can say, “What’s the culture in your hospital like?” So if they say, “I’m gung-ho, but the labor nurses think it’s a stupid thing to do and the hospital is trying to get us to stop doing it because they have a lawsuit and this,” you may have a great doctor or midwife but they may be practicing in a place that isn’t supportive. That’s also an issue. 

Again, I guess there are some people who would lie to you because they “want your business”, but most OBs aren’t like that because if they don’t want to do it, it’s because a) they think it’s wrong, b) they sort of thing it’s okay, but they don’t want to get into a lawsuit, or c) they’re just afraid. So why would they want to hide that from you? It’s the opposite. They would want to tell you upfront. I think if you ask very blunt questions very early, they will tell you. If you have a provider who is uncomfortable, you don’t want to be with them for your VBAC. It’s not a good match. 

Meagan: We talk to our community members about that a lot. Don’t just say, “Do you support VBAC, yes or no?” It’s, “How do you feel about VBAC?” I love the question of, “What is the culture in your labor and delivery unit?” I love, love that. 

Dr. Fox: Usually, this is a good time when open-ended questions are best.

Meagan: Yep, yeah. 

Dr. Fox: Let them talk. Let them cook. They will tell you their thoughts and you can read it very quickly. 

Meagan: Their body language, yeah. 

So circling back to this whole induction thing by 39 weeks, you’re saying that there’s not really any organization that is hard-core supporting this evidence for someone who has had COVID has to have a baby by 39 weeks. 

Dr. Fox: I have not heard that of anybody. Usually, if someone said that, it usually wouldn’t be by 39 weeks. It’s a big thing not to induce people before 39 weeks unless there is a very good reason. 

Meagan: Yeah, and that’s what they’re doing. They’re inducing at 39 weeks or as soon as possible after but I don’t know that anyone is recommending that specifically because of COVID. Again, I’m sure there’s someone who might but I don’t know. Personally, what I would do is if they had COVID, again, I would just check that everything is okay with the placenta. Usually, in later pregnancy, it’s just with an ultrasound and then if everything is fine, I wouldn’t. 

If there is a concern, then it would be based on the concern. There are people who I recommend to get induced at 39 weeks but there is a reason and COVID has not been one of them. 

Meagan: Okay, that’s so good to know. We kind of dabbled into the ARRIVE trial. Can we talk about the 40-week mark? We have seen ever since ARRIVE came out that things have moved up. It’s like 40 weeks is really 39 weeks. 41 weeks is 40. 

Dr. Fox: 39 is the new 40? 

Meagan: 39 is the new 40, yes. It seems to be happening, not everywhere, but it’s happening. We talk about uterine rupture after 40 weeks. Our original 40-week, here we are, we know ACOG suggests or supports going past it, but can we talk about the risk of uterine rupture the further into pregnancy that we go?

Dr. Fox: So there are two risks. Part of the reason for the shift going earlier is not because of the risk of uterine rupture. It’s more of the risk of stillbirth. As you get more pregnant, if you look at just for the baby- I don’t want to say this and be recorded but forget about the mom. 

Meagan: Let’s not think about the mom. 

Dr. Fox: For this question, we’re going to forget about the mom. Mother first, baby second but for this question, you’re just looking at the health of the baby and you look at the timing of delivery. Generally, things get better and better for the baby as you get closer to 39 weeks meaning your baby born at 37 does better than at 36 weeks. A baby born at 38 does better than 37 and at 39 does generally better than 38. 

Once you hit 39, it plateaus and then it starts to diminish meaning that the optimal time for a baby is sometime between 39-41 weeks. As you get past that, it goes down. Part of that is because of stuff after birth like meconium or this and some of it is because some of these babies unfortunately will have stillbirths inside. That’s very, very rare and I’m not saying this to scare anybody, but it happens. As you go past your due date further and further, the risk seems to go up. 

With that said, is it worth inducing because of that? Generally, for a typical, low-risk, healthy person, the difference between 39-41 weeks is very minuscule in terms of the baby. So I don’t typically tell people that if you are low risk, then you need to be induced at 39 or 40. I tell people that 39-41 seems to be very similar for the baby or have very, very slight differences and I leave it to people’s preferences. 

If there’s someone who wants to get the hell out of pregnancy as soon as possible because they are uncomfortable and they have family coming in town or whatever it might be or they are worried about stillbirth, fine. We can go closer to 39 weeks versus if there’s someone who really wants to go into labor on their own, then you wait towards 41 weeks. 

After 41 weeks, the risk really starts going up so there are people who– I don’t really let them– I am okay with them staying past 41 weeks, but generally when we get to 42, pretty much everyone recommends inducing at 42 weeks and pretty much at 41. That’s all because of the baby. 

Now, in that conversation for someone with VBAC, there is a second risk on top of that which is okay, that’s for the baby, but what about for uterine rupture? So there doesn’t seem to be a huge difference between 39, 40, or 41 weeks for uterine rupture. It’s slightly higher if the baby is bigger and it’s slightly higher if you induce. 

So you’re sort of balancing, is it better to induce and have a slightly smaller baby or is it better to wait and go into labor on your own and have a slightly bigger baby also knowing that if you don’t go into labor on your own, now I’m inducing with a slightly bigger baby? That’s part of the risk that you may end up in a situation that is worse. And that again, there isn’t a right or a wrong answer. It’s a conversation. For people whose doctors or midwives won’t induce them, out of principle, the hospital won’t allow it, they won’t allow it, then yeah. You wait as long as they will let you until it’s unsafe for the baby and hope to go into labor on your own. 

In our practice, we do induce people with a prior C-section. It’s a conversation. There are risks that are discussed. They decide, “Is it better to do it earlier? Is it better to do it later?” That’s again, a conversation based on taking on all of the risks. The risk of inducing, probably ballpark adds another 1% so if your risk was 1%, it probably makes it 2%. Again, I could tell you that makes it doubled or I could tell you it makes it 2%. But you know, it increases a little bit. Not so much if they’ve had prior vaginal deliveries. That’s more so if they’ve never had a vaginal delivery. 

The risk of waiting an extra two weeks is also probably less than 1%. These are very small numbers and I don’t want to say pick your poison because neither is really poison, but whichever is sort of more palatable, that’s the one you’ll do. But again, you have to have someone where both options are on the table and for some people, the option to induce is not on the table. 

Meagan: So for someone who is really worried about uterine rupture, going to 41 weeks and maybe not getting induced or trying to go into spontaneous labor at 41 weeks, we shouldn’t be feeling that we have passed that 41 weeks so our chance of uterine rupture just skyrocketed. 

Dr. Fox: No. The chance of uterine rupture doesn’t really go up markedly the more pregnant you get. If you get induced, it goes up a little bit. You have a risk to the baby of waiting.

Meagan: Or a bigger baby. 

Dr. Fox: But the rupture risk is not markedly changed by your gestational age of delivery. Maybe there are slight differences, but nothing crazy. 

Meagan: Okay, that’s good to know for the audience because they ask that a lot. 

Dr. Fox: Right. But a lot of people or some of the doctors want a “controlled setting”. It also depends on what the situation is. Again, I practice in an area where people can usually get to the hospital very quickly if they go into labor. But if you are practicing somewhere where someone has– I actually just had someone. She actually was 2 hours away. She comes to our practice because we are a high-risk practice and she doesn’t want to go somewhere local, fine. She is someone who has two prior C-sections and this. That does play into this because she’s not someone who when she goes into labor is going to be monitored right away. She’s 2-3 hours. 

Meagan: She’s far away. 

Dr. Fox: Yeah, so that is sometimes a factor in these discussions. What you do about it depends but that may be a reason that someone might prefer to have you induced rather than going into labor on your own if they are worried about time to get to the hospital or something like that. Again, usually not relevant for me but sometimes. 

Meagan: More of a controlled setting.

Dr. Fox: Yeah. 

Meagan: You have a lot of knowledge in imaging and testing and all of these things. We’re going to take a little bit of a turn from due dates and all of those things and talk about tests that happen during pregnancy. This is kind of something that comes up a lot. We’ve got early, middle, and late tests that are happening. A couple that is happening in the early stages is genetic testing. It’s becoming a lot more popular and a lot of people are wondering, does this impact my chance of VBAC at all? Does this increase my chance of Cesarean? Can genetic testing impact the mode of birth? 

Is there anything that you feel that our community should know about that early-on test ritual? 

Dr. Fox: It shouldn’t. It really shouldn’t impact anything about the mode of birth. For genetic testing, fortunately, if you get to the point where you are 10, 11, 12, 13 weeks when this is done whether it’s a blood test or an ultrasound, if it’s a screening test or an invasive test like an amnio, again, fortunately, high 90% of people have a baby with no genetic issues whatsoever, thank God. We are very fortunate. 

For the few people who unfortunately have a baby with one of those genetic conditions, genetic screening and testing is information. It’s just to find out before birth. Now obviously, some people get results and choose to terminate pregnancies. Other people get results and choose not to terminate pregnancies. It’s just information they want before birth. That’s also another political discussion, obviously. 

But ultimately, at the end of the day, none of that really impacts the mode of delivery. Occasionally, it impacts the timing of delivery. Sometimes with certain genetic things if there are associated anomalies, then occasionally. So I don’t think it really impacts. It would have to be a very rare case where genetic testing would then somehow preclude someone from a VBAC. 

Meagan: That they would have to have a C-section. 

Dr. Fox: Again, if it precludes someone from having a VBAC, it would also preclude someone from having a vaginal delivery with their first delivery. There are some abnormalities in babies where they are better off being born by C-section but then it has nothing to do with VBAC. That’s just the case. But they are also pretty unusual. Even babies with certain abnormalities can usually be born vaginally safely. But occasionally, there are some that they shouldn’t. But again, not specific to VBAC. That’s just anybody. So yeah. I think if they want to know more about their baby’s genetics, they should do it. They should feel comfortable and if for some reason, they don’t want to know, fine. That’s okay, too but it should not impact VBAC. 

Genetics is the most complicated part of all of prenatal care for patients, for doctors, for everybody. We have 6 hours of podcasting on this and it’s just scratching the surface because it’s complex. It is growing. It’s expanding. So definitely try to get educated on that, but the short answer, it should not affect VBAC. 

Meagan: Yeah, it’s seeming like it’s growing. 

Dr. Fox: Huge, huge. 

Meagan: It’s a popular topic. 

Dr. Fox: We know nothing more about labor than we did 100 years ago, but we know a bajillion times more about genetic testing than we did 100 years ago.

Meagan: Well, and if anyone wants to find out more about genetic testing, then we will make sure to link your podcast or one of the episodes and they can filter through. 

Dr. Fox: Definitely, they’re free. 

Meagan: Okay, so another one, and this is usually done through ultrasound, is the scar thickness. 

Dr. Fox: Mmm, yeah. 

Meagan: What is the evidence? What do you have to say about the scar thickness? We have some providers that are like, “Ope, it’s too thin. You cannot, will not, absolutely will rupture.” They are making very big comments like that. 

Dr. Fox: I just did a consultation for someone on this two days ago. Well, today is Tuesday. Friday, three days ago, whatever it was. Here’s the issue. When you have a C-section, you’re essentially cutting open the uterus, taking out the baby, taking out the placenta, and sewing it back together. If the uterus healed perfectly, exactly the same as before you cut it open, then fine. You don’t have a risk of uterine rupture any more than anyone else in the world who is having a baby. 

But when you cut things open and sew them back together, we know that the integrity of that tissue is always diminished compared to before. That’s true in every part of the body. So when you’re laboring, you are contracting and squeezing and all of that stuff, there is a chance that it would open up. Fortunately, we’ve learned that for people who have this low transverse type of incision, while that is true, the risk of it is pretty low– 1% or less. There are times when it is higher like if you make a different type of incision on them. 

So the question is are there ways to further quantify this risk or to find who is that 1%? Can we predict who that 1% is or is it just pure luck? So someone came up with an idea that, “All right. If I look at the area of the scar where I made the incision and sewed it together either before pregnancy or during pregnancy and I measure it, I can measure the thickness of the muscle.” You’re taking a muscle and sewing it back together. If it’s very thick, the implication is that it’s stronger whereas if it is very thin, the implication is that it’s weaker. 

I would say that is probably true that the thicker it is, the stronger it is and the thinner it is, the weaker it is, but the question is how do you use that practically? Right? Is there a cutoff where I could say, “Okay, if it’s this thickness or greater, the risk of rupture is less than 1% whereas if it’s this thickness and thinner, the risk is more than 1%. It’s 2%. It’s 5%. It’s 10%. It’s 50%.” The problem is that we’ve never been able to identify a good cutoff meaning let’s say a lot of people use 2 or 3 millimeters. Under that number, it is a higher risk. If it’s over that number, it’s a lower risk. 

The problem with that is that there are enough people whose uteruses rupture despite being over 3 millimeters and there are enough people who don’t rupture despite being under 3 millimeters that it doesn’t seem to be any practical or useful cutoff. Most of the studies that have looked at– for example, there is a study where they said, “All right, I’m going to take 1000 women or whatever the number was who have had a prior C-section, and in half of them, I’m going to measure the thickness and do this exercise where if it’s this thick, I will have them VBAC or if it’s this thick, I won’t have them VBAC. And then the other 500, I’m not going to even measure. I’m not going to look.” If you look at those two groups, neither one did better. It sort of indicates that this exercise of measuring the thickness of the incision doesn’t seem to be fruitful. 

I’m sure there is somebody on Earth who you measure the thickness, you see it’s then, you don’t have them VBAC, and you save them a bad outcome, but there are also probably a lot of people who you then said couldn’t VBAC when they would have a perfectly fine VBAC. So the short answer is that nobody knows. There isn’t one standard and that is something that some people use in their practice and some people don’t. In our practice, we don’t formally measure the thickness and make decisions about it. If we see something that looks remarkably unusual, then we have a discussion about it. It depends on your circumstances, but we don’t do that ourselves. 

There are those that do it. Whether they are helping the world or harming the world, I have no idea. Nobody knows. That’s the problem. 

Now, there’s a different situation where you measure the thickness before pregnancy. 

Meagan: That’s what I was just going to ask. Is there a situation where, “Okay. We’re done. We’re not even pregnant and we measure.” 

Dr. Fox: That is something that is an emerging field of research. We do that on certain people who have had multiple C-sections. It’s not often because I want to know if they should VBAC or not. It’s usually if I’m worried about something called a Cesarean scar pregnancy where their pregnancy implants there or if they’re at risk of uterine rupture during pregnancy. There are different cutoffs used. You have to have a very specific test called a saline sonohysterogram where we squirt water into your uterus and measure the thickness of the scar. 

What to do about it, you need surgery to repair that and then what do those people do in pregnancy? This is definitely not standardized and different people do it differently ranging from not doing it at all to doing it very religiously. You still don’t know what is the optimal method for this. Again, we don’t do this test on everybody who has had a C-section between pregnancies. We do it on certain people, but a lot of it is about planning for the pregnancy more than deciding about VBAC or not is what I would say. 

Meagan: If they can or cannot. Okay, that is good to know. And then in the same area, we have some people talking about adhesions. We get adhesions after we have C-sections. If we have really dense adhesions and we’re having issues, does our risk– and we’re seeing this on these ultrasounds– of rupture go up with adhesions? 

Dr. Fox: Adhesions are generally scar tissue in your belly. That’s either between the uterus and other parts of your belly or between layers of your abdominal wall. Number one, we don’t think that they have any impact on the risk of rupture. They make a C-section harder on your surgeon but we don’t usually see them on ultrasound. That’s actually not correct. 

Meagan: People are saying that they are told that. 

Dr. Fox: Adhesion just means that two things are stuck together. 

Meagan: It’s just scar tissue, right? 

Dr. Fox: Yeah. It’s hard to tell if two things are stuck together versus just sitting next to each other on ultrasound. If I showed you a picture of my hands together, you would have no way of knowing if they are superglued together or not unless I tried to pull them apart. 

So it’s the same thing. On ultrasound, we rarely– sometimes, you’ll see that the uterus is tilted in a really weird way and you know it must be scarred or this or that. That’s also prepregnancy. During pregnancy, your uterus grows very, very large and you can’t typically tell who is and who is not going to have scar tissue. It does not usually impact VBAC. 

Also, you rarely have a lot of scar tissue after only one or two C-sections. Usually, it’s if you’ve had three or four or five and we’re not doing VBACs on people who have had three, four, or five C-sections and no vaginal births and so it doesn’t really come into play practically. 

Meagan: Okay, yeah. That’s good to know because people are being told that in these scar thickness visits that, “Oh, and you have a lot of adhesions so your chance of rupture is increased.” 

Dr. Fox: Listen, I don’t have the skill myself to recognize adhesions on ultrasound. I’m not sure if anyone does. I’m not sure if they’re telling people that because maybe– I guess the only way you would know is say someone has had two prior C-sections and they want a VBAC and the person who did their second C-section saw a lot of scar tissue from their first C-section, then they would say, “Listen, I did your second C-section. It’s a mess in there. You’re not a good candidate for VBAC because if you needed an emergency C-section in labor, it would take a long time to do it.” That is a very reasonable discussion to say, “Listen, part of doing your VBAC is having the capability of doing an emergency C-section if it goes wrong or if something bad happens or there is a concern over that.” 

If you know in advance, I can’t do a C-section easily, then it makes it more difficult. For example, that happened to someone who we know has scar tissue, or let’s say someone who had multiple surgeries. Let’s say someone had a tummy tuck which has a lot of scar tissue or they have Crohn’s disease and they had three other surgeries. Let’s say because of the size of the person themselves if they are much larger, then it is harder to do a C-section quickly, then that is a very reasonable concern over VBAC. Listen, if the VBAC goes well, great. But if I have to do a C-section in labor and I have to do it quickly, I can’t do it quickly. 

That’s sort of the reason why hospitals don’t have VBACs because they’re like, “Listen, we don’t have an anesthesiologist 24/7. If you need a C-section, I need 30-60 minutes to get a team in place. That may not be safe.” That’s one of the reasons why smaller community hospitals don’t allow VBACs. It’s not because they’re mean. It’s because they don’t have the proper staffing to address an emergency. 

Now, anybody can have emergency labor, so it’s a problem for everyone, but it’s more common that if you have a prior C-section, then you may have to do something emergently. 

Meagan: Okay, and one of the last and most famous ultrasounds in our community is the third-trimester ultrasound to check baby’s size. In our community, we have a lot of people doubting their body’s ability to give birth because they are told that their babies are too large or their pelvis is too small. La dee dah, we could go on for a long time about that, or that their fluid is too low. We’re getting these third-trimester ultrasounds. One, the question is, is it absolutely necessary? Can someone turn it down? Is it a bad idea to turn it down? And two, if they’re told, “You’re baby is too large. Your fluid is too low,” is it possible to increase their fluid somehow? Is it really possible to know exactly how big that baby is? 

Dr: Fox: To answer that question fully, we need more than the 5 minutes that we have left. I can come back, but the short answer is whether it’s a good idea or not to have that ultrasound is debatable. In our practice, we do it but we have a higher-risk population typically. And I am pretty confident that we interpret the results appropriately. The issue isn’t so much the ultrasound. It’s the interpretation of it. 

Low fluid is a legitimate concern and that’s a concern for the health of the baby because low fluid could indicate a non-functioning placenta or as we said earlier, that your placenta is crapping out. That could be a sign of that. That’s real. That’s legit. 

If the baby is measuring too small, most of them are fine, but the concern is maybe it means that your placenta is crapping out. The baby being too big, there are two issues with that. One is that, especially with big babies, they are less accurate. With smaller babies, we tend to be more accurate. Bigger babies, we tend to be more inaccurate. We may be right that the baby is big, but how big, we’re not that precise. 

And what to do about that. Like you said, most people having a baby can deliver a big baby and everyone’s going to be fine. But yes, there are risks that go up as the baby gets bigger. There is a risk of injury to the baby. There is a risk of injury to the mother and there is a risk of uterine rupture because a) the baby is bigger and b) the labor is likely going to be longer and more difficult which increases the risk. 

Now, whether that should be used as a criterion to prohibit VBAC, again, is debatable. There isn’t a perfect answer to this. I would be less comfortable managing a VBAC if the estimated weight of the baby is 10 pounds over 8 pounds. Do I have to be so uncomfortable that I wouldn’t allow it? It depends on the circumstances, obviously. 

It is a legitimate concern that the baby is measuring big, but again, how confident are we? Those are difficult details. Our ability to assess the size of the pelvis is even worse because the pelvis changes in labor. It’s part of our assessment, but we have the humility to know that we are frequently wrong about that. It’s tough. Listen, if someone had a prior C-section and their story is, “I pushed for 4 hours and this 6-pound baby didn’t come out and they did a C-section,” then in the next pregnancy, I’m estimating a 10-pound baby and the pelvis does not feel so great and the baby is very high, I’m certainly a lot less gungho about it than if they said the opposite. “I pushed for 4 hours for a 10-pound baby,” in the next pregnancy, the pelvis feels really roomy and great and the baby is measuring 6 pounds. 

That’s legitimate. I could be wrong, but that’s information that might be helpful to me. But again, this has to be individualized. There isn’t a perfect answer to this. I wish we could be more scientific. People have tried a lot of different things. There used to be routine X-rays and to see the size of the pelvis and the size of the baby’s head. It didn’t help. The baby’s head changes shape in labor and the pelvis changes shape in labor so we are not precise with this, unfortunately. 

Meagan: No, I love that you said it’s all unique. We’re all individuals. We’re all different and even from one baby to another, we need to remember that it’s always different. 

Dr. Fox: Yeah. Yeah. 

Meagan: Well, I know that we could dive into so much more. There are so many topics, but I really wanted to just thank you so much for taking the time today. I know you’ve got quite the schedule and spent this hour with us answering these questions. 

Dr. Fox: My pleasure. Thank you for inviting me. Thanks for doing what you’re doing. I think it’s great and hopefully, we can continue getting people better information and making good choices. 

Meagan: Yes. We will make sure to link everything to your podcast and your website so people can read more about you. In New York, people can find you. Sometimes, it can be that VBAC people are looking for doctors all of the time. 

Dr. Fox: If you are in New York City, at our practice, we do VBACs so come on over. If we don’t think it’s a good idea, we’ll tell you but if it’s a good idea, we’re on board. 

Meagan: And you do VBAC after two C-sections, you said? 

Dr. Fox: We do. It depends on the exact circumstances, but we don’t prohibit it because of two C-sections. Obviously, there are some people in that category who think it is a better idea than others, but it’s not a hard rule or anything like that. 

Meagan: Okay, good to know. Okay, well thank you so much. Have a wonderful day. 

Dr. Fox: You too. Thank you very much, I appreciate it.

Meagan: Okay, bye. 

Closing

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