Mailbag 33: “What does the Fox say” – 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 am your host, Dr. Nathan Fox, an OBGYN 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.

Welcome to our 33rd “Mailbag” podcast “What Does the Fox Say?” Our first question is from Cindy. “Hi, Dr. Fox. Huge fan of the podcast. Been listening for years since I had my first son in 2023.” Thank you, Cindy. “I just recently gave birth to my second son a bit early at 35 weeks. He’s currently in the NICU doing well, and working on feeding, hoping to get discharged soon. My question is about the potential causes for a late preterm birth like his. When they delivered him, successful VBAC by the way, they told me it looked like he had a placental abruption and there was a large blood clot that came out right behind it. Could that be the reason? Basically, my placenta was failing early. I also had a short cervix and was on progesterone. So, I know that could have influenced this as well. Just curious to hear your thoughts and if we ever really figure these things out and how likely this would be to happen again in a future pregnancy. They did send off my placenta to be studied. Thank you.”

All right. So, Cindy, there’s actually three or four questions within that question, which is terrific, and I’m going to try to go through them one at a time in terms of late preterm birth. So, the first thing for our listeners, preterm birth, we define as any delivery prior to 37 weeks. Again, your due date is 40 weeks. So, 37 weeks is 3 weeks before the due date, and anything earlier than that, we call a preterm birth.

Now, preterm birth, we sometimes will subdivide. One of the ways we subdivide it is whether it was spontaneous versus indicated. Spontaneous would be your body went into labor, you know, had contractions, went into labor, or your water broke. We call those spontaneous. And indicated is, hey, you’re 32, 33, 34, whatever weeks, and because of reasons A, B, and C, we need to deliver the baby either by C-section or by inducing the labor. So, we call that an indicated preterm birth. So, that’s one way we differentiate.

The other way we differentiate and what you might hear is sometimes you’ll hear late preterm birth or plain old preterm birth or early preterm birth or something like that. And, typically, late preterm birth is when someone delivers at 34, 35, or 36 weeks. Why they picked 34 specifically, there’s a lot of reasons. But basically, practically, the main reason we differentiate is that babies who are born in the late preterm birth period, 34, 35, 36 weeks, number one, their outcomes tend to be a lot better, meaning much closer to full-term babies than to preterm, which makes complete sense. And also, a lot of the studies differentiate because there’s certain treatments that will do if someone’s under 34 weeks, but not do in the late preterm birth period, or when they do studies, they will sometimes only include people in prior to 34 weeks or only 34 to 37 weeks. So, there is some sort of value from a research perspective in differentiating those two, and from a practical perspective, it is.

So, your first question was, what is the potential cause or what are the potential causes of late preterm birth? They end up being the same causes as any preterm birth. And typically, the majority of preterm births do fall in that late preterm period. So, if you look at all the studies on preterm birth and all of the causes of preterm birth, they tend to cluster in that 34, 35, 36 time period. Again, this all makes sense, meaning the earlier you’re going to deliver, the more rare that outcome is. So, the causes are the same.

Now, your second question is related to whether your preterm birth was specifically caused by a placental abruption or not. And the short answer is, hard to know for sure, but probably related. And the long answer is, first, I’m going to describe what a placental abruption is for those who don’t know.

So, basically, in the normal course of events in a delivery, what typically happens is mom’s in labor or mom’s having a C-section, whichever way, the baby is delivered, again, either vaginally or by C-section. It’s the same. You clamp the cord, which connects the baby to the placenta and the placenta is attached to the uterus. So, you clamp the cord, you cut the cord, and then at some point after that, the placenta starts to shear off from the wall of the uterus and then comes out.

Again, if it’s a C-section, it’s usually pretty quick because we sort of hurry that along by either squeezing the uterus or grabbing the placenta or pulling on the placenta, whatever it is. And if it’s a vaginal delivery, it’ll happen somewhere between 2 to 30 minutes after the baby’s born, the placenta will start to separate and come out. And that’s what normally happens. And then when the placenta separates from the uterus, that area where the placenta was attached to the uterus starts bleeding. And then the uterus stops bleeding by squeezing, by clamping down, by contracting in that area, and the whole uterus contracts. Okay. So, that’s what normally happens.

A placenta abruption is basically when the order is reversed, meaning the baby’s still inside, has not been delivered, attached to the cord, which is attached to the placenta, but for whatever reason, the placenta starts to separate off the uterine wall before the baby’s born. And then what happens is that portion of the placenta that is sheared off from the uterine wall, that area of the uterus is going to now start bleeding.

And so, when people have a placenta abruption, what they have typically is bleeding. They don’t always have bleeding because it can be something they call concealed where the blood stays inside the uterus, but usually they have bleeding. And then, usually, that blood irritates the uterus and people get painful contractions and they tend to be frequent contractions. And then on top of that, since there’s a portion of the placenta that’s not attached to the uterus and no longer functioning, sometimes you’ll see things like, in the baby’s heart rate, like decelerations, like concerns that the baby’s not getting enough oxygen.

And again, all of these three symptoms, bleeding, painful contractions, and sort of seeing effects in the baby can happen to varying degrees based on how much of the placenta has separated, and factors we don’t understand. We don’t always understand why in one person they may bleed more and have less pain or someone else may bleed less and have more pain. And so, we don’t quite understand some of that variation, but some of it’s related to what’s happening.

If you have a placenta abruption, it can lead to preterm labor and preterm birth. Now, the question is what causes the placental abruption?

In some cases, it’s obvious and it happens from a trauma, like someone who, let’s say, fell down the stairs or someone who was in a car accident or something like that. It can sometimes cause the placenta to shear off. So, that’s a more classic example. Another classic example is certain drugs can do this, like cocaine or something like that. Both of those are not so common in pregnancy, but sometimes it just happens on its own. And we think that those risk factors for it may be related to the health of the placenta. So, for example, it’s more common when there’s other placental problems going on like preeclampsia or fetal growth restriction.

And so, there is some cause and effect questions here, meaning there could be something that…there could be a situation where someone…everything is perfectly fine, then for reasons we don’t understand, they have a placental abruption, and then that causes them to go into labor and have a preterm birth. There’s also situations where there’s something going on with the placenta that we don’t know, we don’t understand, which can lead to a preterm birth, and it can also lead to a placenta abruption.

So, if you think about A and B…you have two things, A and B. So, one of them, in this scenario, A is placental abruption and B is preterm labor. So, you can have a situation where A causes B, the placental abruption causes preterm labor. You can, in theory, have a situation where B causes A, the preterm labor, someone goes into labor, starts contracting and that causes the placenta to separate. So, B causes A. And sometimes you could have another factor like C, which causes both A and B.

And this happens a lot in medicine, when you see two things that are related. So, we know placental abruption and preterm birth are related. We see them coming together. But just because two things come together, you don’t always know did A cause B, did B cause A, or did some other factor C cause both of them? And I think, in your situation, which is common, we don’t know. It’s possible that you had a placenta abruption for reasons we don’t quite understand, which led to you getting contractions and preterm labor. So, that is definitely a possibility.

Then the question would be, why did you get the placental abruption? We don’t know. Or maybe you had preterm labor for causes we don’t quite understand. We frequently don’t understand the causes of preterm labor, and that caused there to be a placental abruption. That’s a possibility. Or maybe there was some underlying factor that was going on prior to both of those things happening that caused them both to happen. The fact that you had a short cervix earlier in pregnancy would indicate there might have been something going on sooner, but exactly what, hard to say. Could there have been some inflammation? We don’t really know.

And so, ultimately, Cindy, I think for you specifically, we don’t know. We don’t really know what caused what and what happened. And so, that also makes it a little bit difficult for us to predict, which is your last question, what’s going to happen in your next pregnancy, right? So, someone has preterm labor and it’s from a cause that is pretty obviously a one-time thing.

So, let’s say, Cindy, your story was a little bit different. And let’s say your story was, I was perfectly fine. Then at 35 weeks, I fell down the stairs. And after that, I started having bleeding and they suspected an abruption. And I went into labor and I delivered at 35 weeks. If that was your story, I would say, okay, I think it’s pretty clear that the fall caused the abruption, the abruption caused the preterm labor. And in your next pregnancy, presumably, if you don’t fall down the stairs, you’re not going to have the placental abruption, you’re not going to have the preterm labor, preterm birth. So, your likelihood of preterm birth, probably not so high in the next pregnancy. Versus someone has a story where everything is going fine. And then at 28 weeks, their water breaks, and then they have contractions, and then they have an abruption, and then they deliver early. And the next pregnancy, we’re like, okay, someone’s water breaks early. It’s more likely to happen again the next pregnancy. So, your risk is higher.

And so, when we’re trying to sort out the next pregnancy in terms of A, what is the likelihood of this happening again? B, what is going to be our plan for the next pregnancy? A lot of it depends on the details. And so, for you, it’s really unclear. So, what I would tell you is that if the primary problem was a placenta abruption and there’s no reason that we know what happened…things, again, like you being in a car crash, falling down the stairs or something like that, there is a chance that it could happen again. Exactly what the chance is, you’ll see different things in literature somewhere around the 20%, 25% range. And were that to happen again, you’d be increased risk for preterm labor and the other complications of placenta abruption. And so, we would watch you a little bit closer in the next pregnancy.

If, let’s say, we think that your primary issue was something like, you know, you had preterm labor first, well, the chance of preterm labor happening again in the next pregnancy is also probably like 20% to 50% in that range. And then, again, we may do different treatments in the next pregnancy related to progesterone and how well we check your cervix and things like that.

So, from what I know about your story, I would say that there is a chance it’s going to happen again in the next pregnancy. Ballpark 20% to 40%, something like that, which means more likely than not it won’t. And generally, in some capacity, you’d be followed closer in the next pregnancy. Now, when you mentioned your placenta being sent off to be studied, whether that’s going to be valuable in trying to figure out what was the primary cause of your problem, sometimes the results of the placental examination will give a hint to what happened and sometimes they won’t. I would say, often, they won’t just for this particular thing, meaning it can confirm that the placenta had signs of an abruption, but it may not tell you exactly why the abruption took place. Thank you, Cindy, for that great question.

Okay. Our next question, also related to preterm labor, is from Michelle. “Hi, Dr. Fox. Thank you for hosting an insightful, informative, and nuanced podcast, and for answering listener questions.” Hey. Thanks, Michelle. “I had a painful third trimester of my first pregnancy, and would like to know what I could expect in a second. I had ‘threatened preterm labor’ with painful regular contractions without any cervical dilation starting at 28 weeks. I received a terbutaline injection to stop the contractions, which helped for about one hour, and was later started on nifedipine every four hours to reduce the pain.”

“I vividly remember my 34-week appointment when an OB I had not yet seen in the practice burst into the room after reviewing my nonstress test and said, ‘You look like you’re in early labor.’ I said, ‘I know, it’s been this way since 28 weeks.’ I lived in what I call early labor with painful contractions lasting about 1 minute, occurring every 5 minutes with no change in my cervix until I delivered at 37 weeks via scheduled C-section for breach position and gestational hypertension. I developed gestational hypertension around 35 weeks, and after birth, was discharged on extended-release nifedipine for my blood pressure. Not sure if that’s related to the contractions.”

“When I asked my OB what to expect in future pregnancies, she said Braxton Hicks tend to start earlier in subsequent pregnancies. And while nothing is a guarantee, she’d guess I’d have contractions starting earlier the second time around. Personally, I find calling what I had Braxton Hicks to be insulting because the contractions were quite painful and very regular. I feel like I’m in a gray zone in the literature because I did not officially have preterm labor since my cervix never dilated. I’m curious about your thoughts on the risk of recurrence and ways to reduce future risk. Thank you.”

All right. Michelle, like our last listener, your question is about preterm labor, preterm birth and there’s actually a bunch of questions in there. So, this is a really good follow-up to the first question we went over. I will try to address it.

So, yes, what you had is called threatened preterm labor. What that basically means or how we mean when we say it is that it’s someone who might be in preterm labor and ultimately is probably not or is not and then sometimes we’ll call that false preterm labor or we’ll call it not preterm labor. But threatened basically means someone’s having contractions.

So, for us, our definition of labor, whether it’s preterm or whether it’s full-term, is someone who has, as you had, painful regular contractions, but it causes the cervix to change, typically dilating, effacing. So, if someone has both of those together, we will say they’re in labor, they’re in preterm labor. Again, preterm are not based on how far pregnant they are. So, what you had was painful regular contractions without any cervical dilation. And so, it would not be defined as preterm labor. So, you could call it threatened preterm labor, you could call it preterm contractions.

Whether they should or shouldn’t be called Braxton Hicks is somewhat semantic. Technically, Braxton Hicks are contractions that don’t cause labor, but I agree with you that the vast majority of people that have Braxton Hicks contractions do not have the experience that you did, which is painful, regular, every five minutes, lasting a minute. Typically, Braxton Hicks are a little bit more irregular. They come and go. They don’t tend to hurt. And so, you’re definitely describing something a little bit more.

We don’t really have a good terminology for what you experienced, and there are people who experience what you did. I mean, there are people who have regular contractions, as you did, every five minutes that are more painful than Braxton Hicks, who are not in labor. And it is a little bit of a conundrum what to do. There is, in people like you, an increased risk of going into labor. Obviously, if you’re contracting painful every five minutes, there is a risk that you are going to go into preterm labor, but not everybody does. And so, what do you do in that situation?

So, it sounds like what your doctors did is they first gave you a medicine called terbutaline and then a medicine called nifedipine. Both of those medicines, at least in this context, are used to…what we call tocolysis or tocolytics. Toco meaning contraction, lysis or lytic meaning to stop. They’re medications that are being used to try to slow down or stop contractions. Terbutaline works from one mechanism. Nifedipine works with another mechanism. Nifedipine is actually a medicine that’s used to lower someone’s blood pressure, but it does have a side effect of relaxing the uterus.

Whether these things are effective or not depends on how you define that. Meaning, there’s pretty good evidence that these medications will not take someone who is otherwise delivering preterm and turn them into someone who is now going to deliver full-term. Meaning, as far as we know, it wasn’t the medication that “got you” to 37 weeks, again, as far as we know from the literature.

So, a lot of people shy away from using them at all, or they only use them for a short period of time. For example, maybe while you’re getting steroids in case someone thinks you are going to deliver early and they’re trying to give you steroids, which takes about 48 hours. Sometimes we’ll use them just during that time period. And using it for an extended period of time, there is potentially some downside to it.

The upside is if it works in terms of your symptoms, you’ll feel better. Even if it’s not going to stop you from delivering early or make you deliver later or improve outcomes in that way, for many people who have symptoms like you, giving them this medicine just makes them feel better. They’re not as worried about the contractions. Maybe they’re able to sleep at night. Maybe they’re able to avoid going to the hospital every other day because they think they’re in labor.

And so, there could be value in that regard. Maybe it helped you in that sense. Maybe it kept you feeling a little bit better. When you’re in 34 weeks and the doctor came in on the nonstress test and said, oh, it looks like you’re in early labor, I assume what was happening is they saw the contractions being…lasting a minute, being frequent, meaning not looking at your face huffing and puffing because they would have seen that before you’re on the nonstress test. But, obviously, you know, the medication either had no impact or maybe it at least helped you feel a little bit better.

But that’s really the best that we have. There’s nothing that we know that’s really going to otherwise slow down those contractions because we don’t really know why they’re coming. Again, if there’s nothing else going on, we’re not 100% sure why they’re happening. So, it’s hard to know what to do about it. There are some people who, either their doctors recommend or they put themselves on some form of modified bed rest.

Again, my attitude is similar to those medications. There’s no evidence that going on bed rest is going to improve outcomes in terms of when the baby’s going to be delivered, in terms of lowering the risk of a preterm birth or anything like that. But if it makes someone feel better, if it reduces the frequency or the pain of the contractions, great, then rest is wonderful. Just like anything else, if you had a headache and lying down makes you feel better, terrific. Nothing wrong with that. So, there isn’t a perfect way to address this, but we just sort of take it person by person, case by case in what to do.

Whether it’s going to happen in your next pregnancy or not is really unknown. I have to agree with your OB that it’s not certain what’s going to happen. Sometimes people have it in one pregnancy and then don’t have it in the next. Although, in my experience and your OB’s experience, people who have this tend to have it in the next pregnancy as well, maybe slightly better, maybe slightly worse, maybe slightly more frequent, maybe slightly less frequent. But I do think it makes sense to plan that it might happen again.

And I don’t have a great answer for you of the way to reduce that risk or what could possibly be done. I think, same situation, you just have to take it as it comes, and just try to figure out the best plan that works for you. I wish there was something better I can give you, but we just don’t know enough about this to really understand what might work and might not work, particularly when you delivered full-term.

If someone has full-blown preterm labor where they have contractions and their cervix did change and we treated them, but they ultimately go on and deliver full-term, 37, 38, 39 weeks, that’s also very complicated what to do in the next pregnancy. Because on the one hand, they had preterm labor. So, that would seem like, oh, they’re at risk for happening again the next pregnancy. On the other hand, they didn’t have a preterm birth, they had a full-term birth. So, that would make them actually lower risk. And it’s a similar conundrum what to do with people like that in the following pregnancy who had sort of all the symptoms or they had the preterm labor, but they ultimately had a full-term birth. And there’s different ways to do it, but there isn’t sort of one specific way.

The other thing that you mentioned was that you developed gestational hypertension, which is where your blood pressure…as you know, where your blood pressure goes up during pregnancy, during delivery or after birth. And ultimately, you ended up needing to be discharged on a blood pressure medicine.

I would say it’s a coincidence that the blood pressure medicine you were discharged on was nifedipine, which is the same medicine they gave you to stop the contractions or to slow down the contractions. It’s a coincidence, but it’s a common coincidence because I would say nifedipine is probably the most common medication used to slow down contractions. And it’s one of the two most common medications used to lower blood pressure in pregnancy. So, it is a coincidence, but it’s not a surprise to me that the medication they use to slow down your contractions is the same one that they used for your blood pressure.

Now, it is not causal, meaning it’s not that since you were on nifedipine for your contractions, that your body somehow became addicted to it or something like that, that when you went off it, your blood pressure went up. That’s not how it works. And so, it’s not that taking the nifedipine earlier in pregnancy caused you to get high blood pressure later in pregnancy needing to go back on the nifedipine. It just happens to be that those are the medications that are most commonly used for those reasons.

Okay. Third and last question for today’s “Mailbag” podcast is from an anonymous listener, not related to preterm birth. We’re going to totally shift gears and talk about something else. “Hi. I’m wondering what your opinion is regarding laser and electrolysis hair removal during pregnancy. I read a lot online that states to stay away due to lack of research. I would love to hear more information regarding this. Thank you for such an interesting and informative podcast.”

All right. Thank you for sending in that question, our anonymous listener. So, I don’t know. A couple of months ago, we had a “Mailbag” podcast where someone asked a question about teeth whitening in pregnancy. And my answer to this is very similar to the teeth whitening. It’s very hard to design a study to prove that these things are safe. And so, the question is, how would it not be safe?

So, for me, when I think about laser hair removal in pregnancy, what could possibly happen that’s going to harm the baby? We’re not electrocuting the body, and we’re not doing anything that…you know, if you get laser hair removal, let’s say, on your face, you’re not going to feel electric shocks running down your arms, legs, and belly. And so, I can’t imagine a scenario where laser hair removal, even if it’s close to the belly, is going to do anything internally to the uterus or to the baby that’s going to be dangerous. And so, I personally…when people ask me, and they ask all the time, about laser hair removal in pregnancy, my sort of joke is always don’t laser the baby. But it’s a joke because I can’t even fathom how it could not be safe.

Now, I always say, can I prove it? Is there a study that’s done that proves that it’s safe? Well, you know, there’s a lot of things we do that don’t have studies that prove that they’re safe in pregnancy, but you just sort of let logic reign. And so, I don’t have an issue with laser hair removal in pregnancy. People ask me about it. I tell them that I think it’s fine. I can’t prove it, but I can’t imagine a situation where it would cause a problem for the baby. Now, obviously, laser hair removal, in theory, you can get a burn or get an infection. That’s sort of standard, but in terms of actually impacting the baby, I don’t have any concerns with it that I can come up with.

All right. Everyone, thank you very much. We’ll see you all next week.

Thank you for listening to the “Healthful Woman” podcast. To learn more about our podcast, please visit our website at www.healthfulwoman.com. If you have any questions about this podcast or any other topic you would like us to address, please feel free to email us at hw@healthfulwoman.com. Have a great day.

The information discussed in “Healthful Woman” is intended for educational uses only. It does not replace medical care from your physician. “Healthful Woman” is meant to expand your knowledge of women’s health and does not replace ongoing care from your regular physician or gynecologist. We encourage you to speak with your doctor about specific diagnoses and treatment options for an effective treatment plan.