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 37th “Mailbag” podcast, “What Does the Fox Say?” Our first question is from Megan [SP], and it’s about placental lakes. “Hi, Dr. Fox. Hello, from Normal, Illinois.” All right. I’m going to digress a little bit and help our listeners know where is Normal, Illinois. So, I grew up in Chicago. Normal, Illinois is in the State of Illinois. It is southwest of Chicago. And if you are driving from St. Louis to Chicago, as we did this past summer, you will pass Normal, Illinois about, I don’t know, 30 or so minutes before you hit Wally’s, which is an amazing place to visit on the way. So, that’s Normal, Illinois. I would also say it’s a little bit wonderful and, in a good way, ironic that someone from a state on the Great Lakes is going to ask about placental lakes.
Okay. Back to the question. “I’ve been listening to your podcast since you started. I believe that was 2020.” All right. Thanks, Megan. “I really appreciate the way you present information. My question is about placental lakes. I’m currently 25 weeks pregnant with my fifth baby.” Strong work. “And at my 20-week anatomy scan, the ultrasound tech mentioned a placental lake. She mentioned the lake and made a note of it. Of course, I went home and Googled it. Google said placental lakes are common in 10% to 20% of ultrasounds. Is this true? I’ve listened to about 1,000 birth stories and never heard anyone talk about one before. When I went to my midwife appointment a few weeks later, she said she hasn’t had any women with one before, and hadn’t seen them on her patients’ ultrasound reports. I would love to hear any information you have on placental lakes as I’m sure, as an MFM, you’ve come across them. I’ve heard having many lakes can be a sign of another issue. Thank you.”
Okay. So, great question. For a little bit of background, the placenta is basically the organ that is used to do a lot of things in pregnancy. But one of them is to transfer nutrients from the mother to the baby, and transfer waste products from the baby to the mother in pregnancy. So, how does the placenta do this?
So, basically, the placenta is a big glob, for lack of a better word, that attaches to the wall of the uterus. And on the baby’s side, there’s the umbilical cord that goes from the baby’s belly button. The cord then hits the placenta on one end. And then the other side of the placenta is attached to the mother’s uterus. And so, there’s blood flow from the mother that goes to the uterus and sort of goes into the placenta and sort of bathes the placenta in the maternal blood. Fine. And then on the baby’s side, the blood goes into the placenta and is in these little blood vessels.
And there’s something in there called cotyledons, which is a fancy word. But basically, there’s a spongy part of the placenta that has within it very, very, very little, tiny blood vessels filled with the baby’s blood. And those blood vessels around them, they’re bathed inside the maternal blood. So, these blood vessels are sort of sitting in a bath of the maternal blood. And what happens is that keeps the baby’s blood and the mother’s blood separate from each other, meaning they don’t normally mix entirely. They’re not just poured in together, but they come right next to each other with a little fine sort of wall between them, which is the blood vessel. And through that wall, oxygen comes into the baby, carbon dioxide comes out, food comes in, waste product comes out. And so, that’s what happens. So, that’s sort of how the placenta works.
And so, if you look at a placenta, either on ultrasound or after birth, there’s these big sort of sections that are spongy. And in between them are spaces, which is where the maternal blood sort of sits. So, on ultrasound, when you see it, you see this gray tissue, that’s the spongy part, it looks on ultrasound. And then the part where the maternal blood is, if you see a section of it, it looks black. That’s how fluid looks on ultrasound.
So, a placental lake is basically the portion of the placenta that’s filled with maternal blood versus the spongy part, which is sort of the fetal blood in the vessels. And placental lakes is when we could see it a little bit more than normal. Normally, you don’t see a bunch of them, but you can. And I will agree with the Google on this one that they are common. They’re seen, I agree, with somewhere up to 20% of ultrasounds. So, yes, we see them all the time. And typically, in isolation, meaning if all you see is a lake or two lakes or whatever it is, it does not mean much. Most of the data suggests it’s not a problem. It doesn’t indicate that anything’s going to happen. There’s nothing you need to do about it and whatnot.
Sometimes, if there are very large placental lakes or there are many placental lakes, more than we would typically see, we’ll make note of that. Exactly what the consequence of that is, is debatable. There are some studies that suggest, if you have a lot of placental lakes or very large placental lakes, it could put the baby at risk for things like fetal growth restriction. And so, maybe we’ll follow up later in pregnancy with another ultrasound just to check. That data is not perfect for a lot of reasons. And one of the reasons is that not everyone describes them lakes on the ultrasound reports. So, you don’t always know if an ultrasound report doesn’t mention it, does that mean it wasn’t there? Or does that mean they just didn’t comment on it? Or when someone mentions it, do they always measure it?
So, there is some uncertainty about this. But basically, if you see a few of them or very small ones, we usually don’t think much of it. If you see many of them or very large ones, we’ll sometimes follow up with ultrasounds later. Whether that’s definitely necessary or not is debatable, but that’s sort of what we do.
There are other times where you see sort of these pockets of blood inside the placenta that is different and not a lake. If there’s high flow in it, that sometimes can indicate different issues related to the placenta. We wouldn’t typically call that a lake in that circumstance. Sometimes, if that’s the case, there is a condition, something called placenta accreta that we talked about before. And when there’s an accreta, sometimes you’ll see something called lacunae, which looks sort of on the surface like a lake because it’s black. But then if you look at the flow, it’s very, very high flow in there, what we call turbulence. So, that’s to be differentiated from lakes. So, that’s another reason this is sometimes complicated because not everyone, when they see this, will differentiate a lacuna from a lake. One has more implications, lacuna, than the other, lake.
So, I hope that answers your questions. Hope you’re enjoying Normal, Illinois, the great State of Illinois. Thank you for sending us that question.
All right. Next question is from Abby, and it’s about VBAC after an arrest of descent cesarean. “Hi, Dr. Fox. I’m five weeks postpartum with my first baby.” Congratulations. “For his delivery, I pushed for five hours, and ended up in a C-section due to failure to progress. It turns out the baby was over 9 pounds and was facing my hip rather than my back, making it harder to descend. I would love to have a VBAC in the future pregnancy, but won’t pursue it. If it is likely, I’ll need another C-section, anyway. My husband and I were not big babies and are of average size. I also am a healthy weight and did not have diabetes before or during pregnancy. I’d love to know if people typically have babies of similar sizes in each pregnancy. Is there a way to determine the baby’s size before delivery next time to help decide what method of delivery to pursue? Do you recommend C-section for large babies, or would VBAC be a reasonable option? Thank you.”
All right. So, there’s a lot to unpack in your question there, Abby. So, first, whenever we’re trying to decide if someone is a good candidate for a VBAC, there are sort of two components to that decision. The first is, if someone has a C-section and they’re going to labor in the next pregnancy, what is the risk associated with that? And the risk we talk about mainly is the risk of something called uterine rupture, which is where the scar on your C-section, the scar of your uterus will open up during the next labor. For most people, that risk is 1% or less. And because of that, the risk is considered reasonable. Again, some people don’t want to take that risk and they don’t VBAC for that reason. That’s fine, but it’s considered reasonable. There are other reasons why the risk might be higher. It does not sound that way for you, although I don’t know your full history, but in general, that’s one component.
The other component of the risk is, well, if I try, am I going to end up with a C-section anyway? So, not so much a risk, but maybe like a consequence, something people would rather avoid if they knew. And so, the other part is how likely is someone to succeed?
If I said to someone, well, you have a 1% risk of uterine rupture, but if you try to VBAC, you’re 98% going to do it vaginally, they may be much more willing to take that 1% risk of uterine rupture versus if I told them, hey, if you try to labor, there’s only a 10% chance you’re going to deliver vaginally anyways. And they’re like, well, why would I take a 1% risk for just a 10% chance of success versus a 90% chance of success?
So, we always try to give people a sense of what is the chance you’re going to succeed when you do a VBAC. And there are different ways to calculate that. There’s sort of using your gestalt, using your experience. There’s various online calculators you can use that take in various components of your history or of your data and to try to give you a more precise answer.
But basically, one of the very important variables is why did you have the C-section in the first place? And it makes a lot of sense. Because let’s say someone had a C-section because they were carrying twins and both of them were breach and they didn’t even labor and they just scheduled a C-section for 37 or 38 weeks. So, that’s one person versus someone like you who pushed for five hours and the baby didn’t come out. So, just logically, you would assume that the first person who never tried to labor, never sort of “had a failed or arrest of labor” or anything like that, probably has a higher chance of success than someone who’s already labored, tried to deliver a baby, pushed for a long time and the baby didn’t come out.
And so, that is correct, statistically. The chances are higher for the first person than the second. And there’s all these possibilities in between. What if someone labored, it got to 6 centimeters and this. And so, you have to take all this into account.
Now, traditionally, someone with what you had, which is called arrest of descent, where you got to fully dilated and you’re in labor, it got to fully dilated, you started pushing, but the baby did not come down and that’s why you had a C-section. Traditionally, people were pretty down on doing a VBAC in that setting thinking, well, if the baby didn’t fit the first time, how is it going to fit the second time? That was sort of the thought process.
And that’s not true because…for several reasons. Number one, as you alluded to, well, the size of the baby might be different. If your first baby is 9 pounds and your second baby is 7 pounds, you would think, geometrically, the second baby is more likely to “fit” than the first baby. And that is true. And so, you are correct. We do try to estimate the baby’s weight in any pregnancy, but certainly, in one where there’s going to be a VBAC, how you estimate the weight, you know, you could do it by ultrasound, which has some level of accuracy, but is not perfect. You could do it by asking the mother herself, hey, you’ve had a 9 pound baby before. Does this baby feel bigger? Does the baby feel smaller? Does the baby feel the same? Which has a level of accuracy as well. You could do it just by feel. The doctor or midwife will put their hands on your belly and say, all right, I think this baby’s about X amount of pounds. Okay. So, that’s one factor.
And so, yes, probably, we would try to check the size of the baby in the next pregnancy because that may impact your decision. Another, which is unrelated to the size of the baby, but sometimes just the head does not come down in a way that’s as conducive to vaginal deliveries. Like you mentioned, the head was facing a different way. Classically, there’s one where the baby faces up towards the ceiling. We call that OP, which stands for occiput posterior. Some people call it sunny side up, which is traditionally a little bit harder to push out or sometimes a baby’s head comes down a little bit crooked, sort of not straight. And we call that asynclitic, which is also a little bit harder to deliver.
So, you can have someone who, in their first pregnancy, they have a situation where they have whatever size baby, and they push for a very long time, doesn’t come out, end up with a C-section. And then the next pregnancy, they can have a baby the exact same size and deliver very easily. And so, it’s not all just the size of the baby and the size of the mother’s pelvis. There’s other factors that come into it.
And so, when we’re counseling people similar to you, they come in and say, hey, my first C-section, I pushed for five hours, what’s my chance of success? Traditionally, we would tell people that the chance of success — and this was based on several studies — was at best 50-50, somewhere between 20% and 50% success rate. Now, you can look at that as glass half-full, glass half-empty, is that good, is that bad? And so, that’s sort of what was traditionally counseled versus someone, like I mentioned earlier, who never really labored and never really “tried” and just had a C-section for another reason, we would tell them their chance of success is somewhere like 70% to 80%, much, much higher.
So, that’s what we would tell people. And different people would decide differently. Some people would say, you know, for a 50-50 chance, it’s not worth it for me. I’d rather have a C-section. And other people would say, hey, for a 50-50 chance, I am going to take the risk, I am going to VBAC. Fine. Both of those decisions could obviously be quite reasonable.
What’s interesting is, in our practice, we noticed after years of doing this, we kind of felt that our success rate was a little bit higher for women who had a C-section for an arrest of descent like you did. That was just sort of our gut that we seem to be…have a higher rate than 50-50. And so, we actually studied this and we published it. This was published in, I think, 2018 or 2019. And we looked at our own experience with women like you who had a first C-section or a C-section in the past for arrest of descent and said, what was our success rate in VBAC? And what we found was our overall success rate for VBAC was actually 84%.
And then we said, okay, let’s sort of take out the women who’ve had a prior vaginal birth. So, sometimes, you’ll have someone who’s had an arrest of descent C-section. And their second pregnancy, they had a successful vaginal delivery. And then we’re seeing them for the third pregnancy, you would expect their success rate to be higher because they’ve already done it before. So, then we sort of isolated women just like you who’s had one prior delivery that was a C-section for arrest of descent and no vaginal deliveries. And we found that the success rate was about 70%, which is pretty good.
And so, when I counsel women…and again, maybe it could just be that our population, for whatever reason, had a better chance of success, or maybe the ones who are really not…were not going to be successful just chose to have a C-section. I don’t really know why we had a higher number than the others, but we did. And so, what I tell people is that the chance of success could be as high as 70%. We don’t know that for sure. And again, people ultimately make a decision about what to do in the next pregnancy based on how much do they want to VBAC, what’s their tolerance for risk, what was the experience of their labor in their C-section. All these things come into it. And, yes, some people will wait and say, hey, if the baby’s tracking for the same size, I think I’ll have a C-section, but the baby’s tracking smaller, I’ll try to deliver vaginally. And all of these are reasonable. And ultimately, it’s a discussion with your midwife, with your doctor about what to do. But I hope that gives you a little bit of background about your particular situation.
Okay. Next question, also related to VBAC and cervical swelling from an anonymous listener. “Love the podcast. Thanks for all the useful information you share. I’ve had two C-sections, both due to the cervix swelling in labor. Both labors have Pitocin and AROM, artificial rupture of membranes, interventions. Question. What causes the cervix to swell? Anything to do about it if it happens. In my situation, is there anything to do before becoming pregnant again to figure out potential causes and/or ways to prevent it from happening again if I ultimately decide to try for a VBAC?”
Okay. So, I think this question is a common one that I get. And I think there’s a misunderstanding of what it means for the cervix to swell. So, I think, sometimes, we as doctors or midwives don’t do a good job at explaining what we’re talking about with patients. And we’ll say to them something like, oh, your cervix is swelling. I think you will need a C-section. And what that implies is you have a problem with your cervix. The cervix is swelling. It’s causing you to need a C-section. And so, like your question, it’s like, well, how do I get my cervix not to swell? What the hell is wrong with my cervix? Why is this happening?
And it’s actually the opposite. When we see the cervix swelling, we call that cervical edema. It’s potentially, not always, but potentially, an indication to us that the labor is not progressing well. So, it’s not that the problem is the cervix and since it’s swelling, you need a C-section or will need a C-section or might need a C-section. It’s the opposite. It’s if I see someone’s cervix swelling, it means that the labor is not progressing well because the head is not coming down and sort of opening and thinning out the cervix.
And so, it was sort of like…traditionally, when I was trained and some of the “old timers” would try to teach how do they diagnose this condition called CPD, cephalopelvic disproportion, which is where, for whatever reason, the head’s not fitting through the pelvis. That itself is a complicated diagnosis, whether it exists or doesn’t exist, whatever. But this is how I was…when they were training me. And they would say, you have to feel the size of the pelvis, try to guess the size of the head, see what’s going on. And they said, when you’re examining the cervix in labor, if you see it starting to swell, that’s a sign that the head’s not fitting because if the head were fitting properly, the cervix wouldn’t swell. It would thin and it would open.
And so, I think that probably the communication to you was…lost something in how it was explained to you. So, in fact, there’s nothing wrong with your cervix. There’s nothing you need to do before getting pregnant again to figure out what’s going on with your cervix. Your cervix is fine. The issue is why did you have two labors that led to C-sections? And that is a different complicated analysis. But the problem isn’t your cervix. The cervix was a symptom of a possible underlying issue that caused the reason to need a C-section. I hope that is helpful.
Okay. Next question is from Eva about fast labors. “Hi, Dr. Fox. Big fan of the podcast. I found it so incredibly informative.” Thank you, Eva. “I had my second baby a few weeks ago,” congratulations, “And had an incredibly fast labor and delivery (two hours from start to finish). I gave birth 12 minutes after I got to the hospital. My question is, since I had such a fast birth once, is it likely that my labor will be fast again? I definitely want at least one more baby and would obviously love for another short and sweet birth. Thank you for this great podcast.”
All right. Eva, congratulations. I’m glad you had a fast labor and delivery, and it was short and sweet. That is awesome. So, we call that precipitous delivery, but fast labor is another great way to put it. The typical sort of research definition is under three hours. The problem is, exactly when you start that clock is unclear. But basically, labors like yours, we call precipitous. It’s fast. It’s not a dangerous thing. Again, for many women, it’s a wonderful thing, particularly if they’re not planning an epidural. For someone who is planning an epidural, sometimes it’s not as great because they often don’t have time to get an epidural, and so, they birth without one. But for women who don’t want an epidural, the faster labor tends to be better for them.
The main issue with it is logistical, is that if your labor is fast and you’re going to deliver before you get to the hospital, whether that’s at home, whether that’s in a car, whatever it is, and we’ve had podcasts about that before. And so, the question is, what do I do? And part of what do I do is, like you asked, is it going to happen again?
And so, the answer is not definitely, but it is more likely. Meaning, someone who’s had a fast labor like you have, in the next pregnancy, it is more likely to be fast than somebody else. It’s not a guarantee. We’ve definitely had people who had a fast labor under three hours and their next one was four to six hours. Or someone, the opposite, they had a six-hour labor and then the next one was two and then the one after that was five.
So, there is variability. Why there’s variability is not exactly clear. Also, why someone’s labor is long versus fast is not entirely clear to us. Is it related to the strength of the contractions? Why would they have stronger contractions one pregnancy versus another? Is it related to the size of the baby, the position of the baby? We don’t really know these things. It’s amazing that we don’t know this, but we don’t.
And so, what I tell women in this circumstance is, you’re at risk for this happening again. It does not mean it will happen again. And then because of that, we need to decide what we’re going to do about that. And that could mean it’s different for every person based on how far they live from the hospital, you know, all of these things. Sometimes, for women, it’s, you know, hey, first sign of anything, just start heading in, call us on the way. Just try to make sure that, you know, you’re…assuming you don’t want to deliver in your car, I think most people don’t, that you’re in the hospital before you deliver. For other women, it’s, hey, I don’t want that at all. At a certain point, maybe 39 weeks or whatever, I’m going to come in before labor, scheduled, have an induction, so at least I know I’ll be in the hospital. And again, whether to do that, whether or not to do that, when to do it, depends on a lot of individual parameters and circumstances. But, yes, I would assume that if you have another child, you will probably have a fast labor, but not definitively. So, it’s hard to say for sure.
Okay. Our last question for today is from Rachel, and it’s about pregnancy while nursing. “I’m nursing my nine-month-old and just got a positive pregnancy test. I’ve been taking folic acid for the past few week and started my prenatal a few days ago. I’m worried about my fetus not getting enough nutrients due to breastfeeding. I try to eat well. In general, I do some days better than others. I’m specifically scared of spina bifida, no specific reason. Any thoughts?”
So, the idea about whether it is or is not healthy, safe, whatever you want to call it, to continue nursing while you are now pregnant again is a longstanding question. There was traditionally a recommendation that once you get pregnant again, you should stop nursing. There’s been pushback against that recommendation, saying it’s not necessary. Obviously, a lot of this is also related to choice. Some women really prefer to breastfeed as long as possible. Other women, you know, do not. And they’re like, all right, I’m pregnant again. It’s time to stop, and that’s fine. And again, there’s so much that goes into that.
In terms of the actual specific risk, like what is the risk of nursing, continuing to nurse while you get pregnant, some of it will also depend on whether you’re nursing exclusively versus periodically. And there are some studies that suggest that someone who’s exclusively nursing gets pregnant might have an increased risk of early miscarriage. It’s not been shown in all studies. It’s not entirely clear if that’s true or not. And exactly how that would happen is not entirely clear.
You know, if you think about it, the thought process is that if you’re nursing, number one, the nutrients that would normally go to the mother or to the developing baby are going to the baby who’s nursing. So, that’s one thought of a potential reason why it can increase the risk. The other is that when you nurse, the brain, the mother’s brain, releases something called oxytocin. So, after delivery, birth, when someone’s nursing, they’ll frequently feel cramping in their belly. That’s oxytocin, aka Pitocin, which will cause contractions.
It’s hard to imagine how either of those would cause an early miscarriage. It’s not like there’s enough Pitocin that would cause someone to miscarry a normal pregnancy. And it’s hard to imagine that nursing will cause the mother to be malnourished to the point that it would cause a miscarriage. I mean, many, many women in early pregnancy are not able to eat or drink much because of nausea, vomiting, even hyperemesis where it’s severe. And it’s not so much a risk of miscarriage. It’s more of a risk to the mother.
So, I don’t typically tell women that if they continue to nurse, they increase the risk of miscarriage. I think the data does not truly support that statement. And if a woman really wants to continue nursing, I think, probably, the data supports that it’s not going to increase her risk of miscarriage.
In terms of your concern about increasing the risk of birth defects and reducing the amount of folic acid that you’re taking your blood, I don’t know of any data that suggests that nursing in early pregnancy will increase the risk of birth defects like spina bifida to this developing baby. That also seems highly unlikely to be plausible, just given it’s not that all the folic acid and nutrients go through the breastmilk. The mother’s body still has plenty of it. So, that does not make a lot of sense to me.
There is some potential risk and some data supporting that the more someone nurses during early pregnancy, there is a higher chance of fetal growth restriction later in pregnancy, which does make some sense because whatever calories the mother is getting, a certain portion of them are going to her baby who’s nursing. And therefore, it’s just like if someone ate less or gained less weight in pregnancy, there’s a higher risk of something called fetal growth restriction at the end of pregnancy.
So, there is some plausibility to that. It’s not generally a reason that someone would stop breastfeeding if they really wanted to do it. Maybe in that circumstance, we would just focus on maybe getting more calories into her. Maybe she’d have to eat more, increase whatever protein or something like that. Or it also might depend, was she at risk for growth restriction in the first place? And again, how much does she want to continue nursing and this and all that comes into it.
But I think in a high level, most of the data suggests it’s not particularly unsafe for the mother or for the developing baby, fetus, for her to continue nursing her baby. There are some potential things to look out for, but generally not such a high risk that we would tell everyone they have to stop anymore. And I think that’s the general consensus out there.
All right, everyone. Thank you. This is another great “Mailbag” podcast. Please keep sending in your questions. We’ll see you all next week.
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