Hi, everyone. On today’s podcast, we’re going to talk about the evidence on inducing labor for going past your due date.
Welcome to the Evidence Based Birth podcast. My name is Rebecca Dekker, and I’m a nurse with my PhD and the founder of Evidence Based Birth. Join me each week as we work together to get evidence-based information into the hands of families and professionals around the world. As a reminder, this information is not medical advice. See ebbirth.com/disclaimer for more details.
Hi, everyone. On today’s podcast, we’re going to talk about the evidence on inducing versus waiting for labor when you’re going past your due date. I’m going to be joined by Anna Bertone, MPH, our Research Editor at Evidence Based Birth to talk about this topic.
Before we get started, I have a quick announcement, and that is next week we are hosting free webinars for the public all about the Evidence Based Birth Childbirth Class. On Monday, March 2, we’ll host a special webinar just for parents. We’ll give you a peek behind the scenes at what it’s like to take our Evidence Based Birth Childbirth Class. Then on Tuesday, March 3, we’ll have a special webinar just for birth professionals to give you a tour of the Evidence Based Birth Childbirth Class so that you can decide if it’s something you’d like to recommend to your clients or not. You can register for these free webinars at evidencebasedbirth.com/childbirthclasswebinar. That’s all one word /childbirthclasswebinar.
All right, now back to the topic at hand, inducing labor for going past your due dates. Now before we begin, I do want to give a brief trigger warning. In our discussion about the research evidence on this topic, we will be talking about stillbirth and newborn death. So there has been a ton of new research on the evidence on induction versus waiting for labor when you go past your due date. So much research, in fact, that we have decided to separate our Signature Article on due dates into two separate articles.
So we still have the original article, The Evidence on Due Dates, which you can find at ebbirth.com/duedates. And although we updated that article a little bit, it’s remained very similar to previous additions. It talks about the length of a normal pregnancy, factors that can make you more or less likely to have a long pregnancy, et cetera. But then we separated out the research on induction into a new article that you can find at ebbirth.com/inducingduedates. This is a peer-reviewed article that covers all of the research on induction versus something called “expectant management” for going past your due date. And in today’s podcast, we’re going to update you on the latest info that we found for that article.
Just a heads up, we will not be covering the research evidence on inducing at 39 weeks. We already covered the ARRIVE study, a randomized trial that looked at induction versus expectant management for 39 weeks of pregnancy in episode 10 of the Evidence Based Birth podcasts. And just a tip, if you’re having trouble finding any of our earlier episodes of this podcast, iTunes has stopped showing the earliest podcasts, but they’re still out there and you can find them on Spotify and any other podcasting app. You can also find info about the ARRIVE study at ebbirth.com/arrive.
So we’re not going to talk about induction at 39 weeks. Instead, we’re going to be focusing on the evidence on induction versus waiting for labor once you reach 41 weeks. And to do so, we’re going to talk with our Research Editor, Anna. So welcome, Anna, to the Evidence Based Birth podcasts.
Anna Bertone: Thank you! I’m glad to be on the podcast again.
So I want to start by explaining to our audience a little bit kind of about the background of why this topic is important. Inductions for non-medical reasons have been on the rise in the United States and all around the world for the past 30 years. And increasingly, more people who are pregnant are being induced for reaching their estimated due date. So we really want to cover the benefits and risks of elective induction for going past your estimated due date. And we’ll also talk about whether or not your goals and preferences for your birth matter, which of course they do, but that kind of plays a role as well.
So how often are people induced for going past their due date? Well, we don’t know for sure because this hasn’t been measured recently. But according to the 2013 Listening to Mothers III survey, which was now published about seven years ago, more than 4 out of 10 mothers in the U.S. said that their care provider tried to induce labor. Inducing labor for going past your due date was one of the most common reasons for an induction. Out of everyone who had an induction in this study, 44% said they were induced because their baby was full term and it was close to the due date. Another 18% said that they were induced because the healthcare provider was concerned that the mother was overdue.
The Centers for Disease Control in the U.S. also reported in 2018 that about 27% of people had their labor induced, but we think that number is probably low and that the percentage of people who have labor induced is under-reported in the Vital Statistics Program in the United States. So Anna, can you talk a little bit about why there’s so much controversy over this concept of electively inducing labor once you go past your due date?
Anna Bertone: So why is there so much controversy about elective induction? Elective inductions by definition are labor inductions that do not have a clear medical reason for taking place. They occur for social reasons, like the provider wanting the mother to give birth before the provider goes out of town or for other non-medical reasons like the pregnancy getting uncomfortable and for the mother’s convenience. But there’s also a gray zone about what constitutes an elective induction. Many providers only consider an induction to be “elective” when the mother is healthy, pregnant with a single baby, and less than 41 weeks pregnant. The gray zone is that sometimes when the pregnancy goes past 41 weeks, some providers consider that to be a medically indicated induction rather than an elective induction. But in general, inductions are considered medically indicated when there are accepted medical problems or complications with the pregnancy that make it less safe to continue the pregnancy.
For many years, and I remember when I first entered the birth world in 2012, a lot of people talked about the fact that if you have an induction it doubles your chance of cesarean. And then all of a sudden there were people saying that wasn’t true. So can you talk a little bit about that controversy?
Anna Bertone: So for many years, the common belief was that elective induction doubles the cesarean rate, especially in first-time mothers. But researchers nowadays consider those earlier studies to be flawed. In the earlier studies, what they would do is they would compare people assigned to elective induction to people who went into spontaneous labor. Nowadays, they don’t compare those two groups anymore. They compare people assigned to elective induction to the people assigned to what’s called expectant management, or in other words waiting for labor. And in that group, the person could either go into spontaneous labor or they could require an induction for medical reasons (so that would be a medically indicated induction), or they could choose elective induction further along in the pregnancy.
So that’s a subtle difference but an important one because in the earlier studies they compared elective induction to spontaneous labor. But you don’t have the choice to go into spontaneous labor today. Your choice is to be induced today or to wait for labor to start. And sometimes during that waiting period you might develop complications that require an induction, or you might change your mind and decide to have an elective induction, or you might go into spontaneous labor.
Anna Bertone: Right. So nowadays, we compare a group assigned to elective induction to a group assigned to expectant management. One example of this was the ARRIVE trial.
The ARRIVE trial was a study comparing elective induction at 39 weeks versus expectant management. We’re not going to go into that trial in detail because we already covered it in detail in episode 10 of the Evidence Based Birth podcasts. But they actually found a lower risk of cesarean in the elective induction group. Researchers think that had to do with the fact that of the people in the expectant management group, more of them developed problems with blood pressure that required medical inductions and increased risk for complications. So again, that just kind of goes to show you that it does make a difference when you compare elective induction to expectant management.
Although, one thing you have to keep in mind with the ARRIVE study is that they had a very low cesarean rate in both groups compared to some settings. The cesarean rate was 19% in the elective induction group versus 22% in the expectant management group. So those research results cannot probably be generalized to settings with extremely high cesarean rates or high cesarean rates with inductions. We have some, for example, some professional members at Evidence Based Birth who talked to us about where they’re practicing and how high the cesarean rates are with the elective inductions there. So I think you have to be careful how you generalize or apply that data from the ARRIVE study, and we talk more about that in episode 10 of the podcast.
Which leads me to another point, and that is some cautions about the evidence. When I say generalize, that means taking research from a research study, and seeing if you can apply that to where people are giving birth in your community. So it’s important to understand that there are some major drawbacks to some of the research that we’re going to be talking about. Many of the studies are carried out in countries or time periods where there are low cesarean rates. So when that happens, when a study is carried out in a setting where culturally there’s low C-section rates, that might not apply to a hospital with high cesarean rates. If your hospital has high rates of “failed inductions” and strict time limits on the length of labor, then the evidence in these studies may not apply to you because induction might be more risky in your community hospital.
Also, another disclaimer about the evidence, in these trials, people are randomly assigned to induction or expectant management. And it’s important to remember that the people assigned to expectant management do not always go into labor spontaneously. There’s a mix of people in that group. Some of them do have a spontaneous labor. Others have an elective induction later on, and others have a medical induction for complications.
Also, you have to look at what they’re doing for fetal testing in the studies. In some studies there’s lots of fetal testing going on in the expectant management group. However, we’re going to talk about one of the studies where they were not doing any standard fetal monitoring during expected management. So those results might not apply to your community if your community does the fetal monitoring, and the study did not have fetal monitoring.
Finally, another disclaimer about the research evidence is that the induction protocols vary from study to study, and even within studies themselves. So knowing what the protocol was for induction in that study can be very helpful to decide if this is going to apply to your unique situation in your local community or not.
So with all of those disclaimers being said, there’s been quite a lot of new research in the past year about induction at 41 weeks. So Anna, can you talk about one of the most recent studies? Let’s talk about the INDEX trial from the Netherlands. There were two trials that came out in 2019, two large randomized control trials. Let’s talk about the INDEX one first.
Anna Bertone: Sure. So the INDEX trial was from the Netherlands. INDEX stands for induction at 41 weeks, expectant management until 42 weeks. This was a large multicenter trial. It was conducted at 123 midwifery practices and 45 hospitals. Most of these pregnancies were managed by midwives.
…So this was the midwifery-led model of care-
Anna Bertone: Exactly.
… which is very different than in the United States which is typically an obstetrician-led care model.
Anna Bertone: The researchers randomly assigned a total of 1,801 pregnant people to either induction at 41 weeks and zero to one days or to wait for labor until 42 weeks and zero days, which is called expectant management. The reason they were able to conduct this study in the Netherlands and got ethical approval for it is because it was standard practice for them to not induce labor before 42 weeks with an uncomplicated pregnancy.
…Whereas in the U.S. it’s rare to see someone go to 42 weeks, in the Netherlands, they typically won’t induce you unless there’s medical reasons until you get to 42 weeks –
Anna Bertone: Exactly. So the mothers were enrolled in the study between 2012 and 2016. Everyone had to be healthy, and pregnant with single, head-down babies. The gestational ages were estimated with ultrasound before 16 weeks of pregnancy. They excluded people with a prior cesarean, with high blood pressure disorders, with expected problems with the baby’s growth, abnormal fetal heart rate, or known fetal malformations (congenital anomalies). In both groups, cervical ripening and induction methods depended on local protocol. It’s like what Rebecca was talking about earlier. There wasn’t a standard protocol to apply to both groups in this study when it came to cervical ripening and induction. It was based on local protocol. And this is an important weakness of the study because the providers might’ve managed labor inductions differently based on whether someone was being electively induced or was assigned to the expectant management group. It also limits the study’s generalizability, which means our ability to apply the results of this study to the population at large because providers don’t have an induction protocol that they can replicate.
…So we can learn from what happened in this study, but it’s difficult for us to apply it to across the board because there’s no specific induction protocol that could be followed –
Anna Bertone: Yeah. What happened was in the elective induction group, 29% of the participants went into labor before their induction and 71% were induced. Then in the expectant management group, 74% of the participants went into labor spontaneously before their planned induction and 26% were induced.
…And before we talk about how long the pregnancies were, I think it’s important for people to understand that when you have a randomized controlled trial like this the researchers do something called intent to treat analysis. So it doesn’t matter what type of birth they had, whether it was a spontaneous labor or a medical induction, the data were analyzed depending on which group you were originally assigned to. So if you were assigned to an elective induction but you happen to just quick go into labor on your own before the induction, you were still grouped with everyone in the elective induction group and vice versa. So that’s just an important distinction for people to understand. –
Anna Bertone: Yes. What happened with these results is that the median pregnancy was only two days shorter in the elective induction group compared to the expectant management group. This is interesting because they still found a difference between these two groups, but-
…And this is important because a lot of people ask us like, “Well, I only want to wait one more day, or two more days, or three or four more days,” but they’re saying by decreasing the length of the pregnancy by two days they found significant results. So what did they find in the INDEX trial? –
Anna Bertone: So for mothers, they found that there was no difference in the cesarean rates. This was taking place in a country with low cesarean rates. It was a midwifery model of care and the rates were very low in both groups (11%).
They only had an 11% cesarean rate then?
Anna Bertone: Yeah. They also had an outcome called a composite outcome, which is a combined outcome for mothers, and there was no difference in that measure either. They were looking for things like excessive bleeding after birth, manual removal of the placenta, severe tears, intensive care admission, and maternal death, and they didn’t find a difference in those things. There were no maternal deaths in either group. So as far as the bad outcomes for the mothers, there were about 11% to 14% in both groups, but not different.
…And what about for the babies then? –
Anna Bertone: And then for the babies, the babies in the elective induction group had a lower composite outcome rate. And in this composite outcome, what they were looking at was perinatal death, Apgar score less than seven at five minutes, low pH, meconium aspiration syndrome, nerve injury, brain bleeds, or admission to a NICU. And here they found a lower composite adverse outcome rate with the babies in the elective induction group (1.7% versus 3.1%).
And why do they think that outcome was better with the elective induction group?
Anna Bertone: They think that it was mostly due to the lower rate of Apgar scores less than seven at five minutes, and that probably contributed the most to having a lower adverse outcome rate with the babies in the elective induction group. The author’s note that there was no difference in rates of Apgar score less than four at five minutes, but they found that the combined outcome was still lower in the elective induction group if they used an Apgar score of less than four at five minutes and excluded fetal malformations. So basically, the babies in the elective induction group had better Apgar scores overall.
…And what about stillbirths? Because that’s like the main reason they’re doing these kinds of elective inductions, is to lower the risk of stillbirth. –
Anna Bertone: Yep. And they did not find a difference in stillbirth in this study. There was one stillbirth that occurred in the elective induction group. It was at 40 weeks and six days, before the mother was induced. Then, there were two stillbirths that occurred in the expectant management group while the mothers were waiting for labor.
Anna Bertone: I looked for a few more details about those stillbirths because I was interested in that. Of the two stillbirths that occurred in the expectant management group, one was a small for gestational age baby at 41 weeks and three days to a first-time mother. The other one was to a mother with a prior birth, and that was at 41 weeks and four days. The mother’s placenta showed signs of infection (infection of the membranes). Then, the one stillbirth that occurred at in the elective induction group at 41 weeks was to an experienced mother (someone who had already had given birth before), and that was at 40 weeks and six days, and there was no explanation for that one. But with two versus one, they didn’t find a significant differences in stillbirths between those groups.
And what was the protocol for fetal monitoring in that study?
Anna Bertone: There was no protocol for fetal monitoring. It depended on local guidelines, just like the induction and cervical ripening protocol. But the study authors say that fetal monitoring and assessment of amniotic fluid levels was typically done between 41 and 42 weeks.
So how would you sum up the results of this INDEX study then?
Anna Bertone: They found that elective induction at 41 weeks resulted in similar cesarean rates and less overall bad outcomes for babies compared to waiting for labor until 42 weeks. However, they say that the absolute risk of a bad outcome happening was low in both groups. It was 1.7% in the elective induction group versus 3.1% in the expectant management group (the group that waited until 42 weeks).
All right. Well, the next study we wanted to talk about was the SWEPIS trial from Sweden, also published in 2019, also coming out of Europe. It’s S-W-E-P-I-S, and it stands for the Swedish post-term induction study, or SWEPIS. It got a lot of media attention with headlines like … There was one that said, “Post-term pregnancy research canceled after six babies died.” And it is true that this study was ended early after deaths in the study. The researchers intended to enroll 10,000 mothers from multiple centers across Sweden, but they ended up stopping the study with about 1,380 people in each group after their data safety and monitoring board found a significant difference in perinatal death between the groups.
Data safety and monitoring boards are basically a board that keeps track of what’s going on in the study. They get interim reports. And if they see any concerning safety issues, they have the power to stop the studies. That’s a standard part of a lot of randomized controlled trials is to have one of these safety boards.
Similar to the INDEX trial in the Netherlands, in Sweden, labor is typically not induced before 42 weeks if you have an uncomplicated pregnancy. Also similar to the Netherlands, in Sweden, midwives manage most of the pregnancies and births. It’s a midwifery-led model of care.
The purpose of the SWEPIS study was to compare elective induction at 41 weeks and zero to two days versus expectant management and induction at 42 weeks and zero to one day if the mother hadn’t gone into labor by that point. The study was carried out in the years 2015 to 2018. The researchers enrolled healthy mothers with single babies in head-first position. They had accurate gestational ages. They excluded people with a prior cesarean, diabetes, and other complications such as high blood pressure, small for gestational age, or known fetal malformations.
There is a pretty low stillbirth rate in Sweden, so they thought they would need about 10,000 people to see a difference between groups, but they ended up not needing nearly that many people to find a difference in stillbirth rates. One of the big strengths of the SWEPIS trial is that in contrast to the INDEX trial, in the SWEPIS trial they defined an induction protocol and they used that same protocol with everyone in the elective induction group and everyone in the expected management group who had an induction. The protocol was basically if the mother’s cervix was already ripe, they simply broke her water and gave her oxytocin as needed by IV. If the mother’s cervix was not ripe or the baby’s head was not engaged, they used mechanical methods or Misoprostol, or prostaglandins, or oxytocin, but they did cervical ripening first.
In the elective induction group, most of the people were induced. 86% had their labor induced. 14% went into labor spontaneously before the induction. In the expectant management group, 67% of them went into labor spontaneously and 33% ended up with an induction. Similar to the INDEX trial, there was a really tiny difference in the length of pregnancy between groups. Pregnancy in the elective induction group was in general only three days shorter than pregnancy in the expectant management group, but yet they did go on to find significant differences.
So what the SWEPIS trial found was that for babies – this is why this study was stopped early – there were five stillbirths and one early newborn deaths in the expectant management group out of 1,379 participants for a death rate of 4.4 deaths per 1,000 women. There were zero deaths in the elective induction group out of 1,381 participants. All five stillbirths in the expectant management group happened between 41 weeks, two days and 41 weeks, six days. Three of the stillbirths had no known explanation. One was for a baby that was small for gestational age. The other was with a baby who had a heart defect. There was one newborn death that occurred four days after birth due to multiple organ failure in a baby that was large for gestational age.
The authors mentioned that when complications are present at the end of pregnancy, such as problems of the placenta, or the umbilical cord, or fetal growth, these problems may become increasingly important as each day of pregnancy progresses, which they believe is why they found a higher death rate with expectant management past 41 weeks.
Another key finding of the study was that all of these deaths occurred to first-time mothers, which suggests that 41-week induction may be especially beneficial for babies of first-time mothers. They found that it only took 230 inductions at 41 weeks to prevent one death for a baby, and this was a much lower number than previously thought. If you remember, though, as Anna was saying, the INDEX trial did not find a significant difference in death between the induction group and the expectant management group. We think the reason the SWEPIS study found a difference was because it was a larger study, it was better able to detect differences in rare outcomes like death. Also, with the SWEPIS study, there might not have been as good fetal monitoring. So it’s possible that the better fetal monitoring of participants between 41 weeks and 42 weeks in the INDEX trial might’ve been protective, leading to fewer perinatal deaths. We can’t be certain though because there were no fetal monitoring protocols in either trial.
Another thing to note is that participants in the SWEPIS expectant management group tended to give a birth a little later than the participants in the INDEX expectant management group. That might help explain the higher perinatal death rate in the expectant management group in SWEPIS. They did not find a difference in what they call the composite adverse perinatal outcome, which included death, low Apgar scores, low pH, brain bleeds, brain injury, seizures, and several other major complications, but there was that significant difference in perinatal death (either having a stillbirth or newborn death).
Also, the elective induction babies were less likely to have an admission to intensive care, 4% versus 5.9%. They had fewer cases of jaundice, 1.2% versus 2.3%, and fewer of them were big babies, 4.9% versus 8.3%.
For mothers, the outcomes were overall pretty good. There were no differences in cesarean rates similar to the other trial. The cesarean rate in this study in both groups was about 10% to 11%. More mothers in the elective induction group had an inflammation of the inner lining of the uterus called endometritis, 1.3% versus 0.4%. And on the other hand, more mothers in the expected management group developed high blood pressure, 3% versus 1.4%. They also interviewed the women in both groups and they found that the mothers in the expectant management group really struggled with negative thoughts. They described feeling in limbo while they waited to go into labor. So Anna, can you talk a little bit about the fetal monitoring in this study and how it may have differed from the other study?
Anna Bertone: Sure. Fetal monitoring in this study was done per local guidelines. So there was no study protocol for fetal monitoring during the 41st week of pregnancy. However, the mothers recruited from one region of Sweden, called the Stockholm region, which made up about half the people in the study, had ultrasound measurements of their amniotic fluid volume and abdominal diameter at 41 weeks, whereas the people that came from the other areas of Sweden in the study did not receive these assessments regularly. None of the six deaths that occurred in this study occurred in the Stockholm region of Sweden where they received this type of fetal monitoring, which leaves us with the question of how important was this fetal monitoring. Could it have made the difference between the Stockholm region participants not experiencing fetal deaths whereas participants from other regions did?
Anna Bertone: So that’s just an important thing to keep in mind with this study is that the fetal monitoring may have made a difference as far as the perinatal outcomes. It also means that the results of the SWEPIS study might not apply equally to mothers who receive fetal monitoring at the end of pregnancy, specifically during that 41st week of pregnancy which seems to be the really critical time period. Another thing, all of the perinatal deaths in this study occurred to first-time mothers, which tells us that the results might not apply equally to mothers who have already given birth before.
…So in the SWEPIS study, out of the mothers in the study who had already given birth before and were having a subsequent baby, none of them experienced this stillbirth or newborn death, correct?
Anna Bertone: Correct. Yes.
Okay. So all of the perinatal deaths occurred to first-time mothers.
Anna Bertone: And the first-time mothers, by the way, they only made up about half of the participants in the sample, so it was about a 50/50 split.
So all of the fetal and newborn deaths from this study came from first-time mothers who lived in the areas of Sweden that did not do any prescribed fetal monitoring during that 41st week of pregnancy.
Anna Bertone: That’s my understanding. Correct.
Okay. So those are the two big randomized trials that came out in 2019. Before they were published, there was a 2018 Cochrane meta-analysis. Anna, I was wondering if you could talk a little bit about that. This study did not include the SWEPIS and the INDEX trials, but we still wanted to talk about it in our article. So can you explain to our listeners a little bit about this Cochrane review?
Anna Bertone: Sure. There was a 2018 Cochrane review and meta-analysis by Middleton. Unlike these randomized control trials that we were just talking about, they didn’t focus specifically on the 41st week of pregnancy versus the 42nd week of pregnancy. It was much more broad than that. What they did was they looked at people who were electively induced at some point, and compared them to people who waited for labor to start on its own until some point. So there was a much more broad range of gestational ages there. But they included 30 randomized control trials with over 12,000 mothers, and they compared a policy of induction at or beyond term versus expectant management. All of the trials took place in Norway, China, Thailand, the U.S., Austria, Turkey, Canada, the UK, India, Tunisia, Finland, Spain, Sweden, and the Netherlands.
So it’s quite a global sample.
Anna Bertone: Yes. But one study in this meta-analysis really dominated and accounted for about 75% of the data, and that was the Hannah post-term trial that I think Rebecca is going to be talking about soon. Because that one trial dominated this meta-analysis so much, most of the data was on giving birth at 41 weeks or later.
And they did not include the ARRIVE trial in this meta-analysis.
Anna Bertone: Right. They didn’t include the ARRIVE, INDEX, or SWEPIS trials. So in its next update, it’s going to be updated with those three randomized control trials. But they did include 30 other randomized control trials. What they found was that a policy of induction at term or beyond term was linked to 67% fewer perinatal deaths compared to expectant management. So that was two deaths with induction at or beyond term versus 16 deaths in the people assigned to expected management.
Anna Bertone: The Hannah post-term trial excluded deaths due to fetal malformations, but some of the smaller trials that were included in the Cochrane meta-analysis did not. So if we exclude the three deaths from severe fetal malformations, then the final count is one death in the induction group and 14 in the expectant management group. So it doesn’t change the results too much overall to exclude fetal malformations. Overall, they found that the number needed to treat was 426 people with induction at or beyond term to prevent one perinatal death. Specifically, there were fewer stillbirths with a policy of induction at or beyond term.
Which was a different number needed to treat than the SWEPIS trial, which found only took 230 inductions at 41 weeks to prevent one perinatal death.
Anna Bertone: Yeah. I think part of the reason the SWEPIS trial was so groundbreaking and got so much media attention is because it did find a lower number needed to treat than had been found previously. So the absolute risk of perinatal death was 3.2 per 1,000 births with the policy of expected management versus 0.4 deaths per 1,000 births with the policy of induction at or beyond term. They found that a policy of induction was linked to slightly fewer cesareans compared to expectant management, 16.3% versus 18.4%.
Anna Bertone: Fewer babies assigned to induction had Apgar scores less than seven at five minutes compared to those assigned to expectant management. They didn’t find any differences between the groups with the rate of forceps or vacuum assistance at birth, perinatal trauma, excessive bleeding after birth, total length of hospital stay for the mother, newborn intensive care admissions, or newborn trauma. The authors concluded that individualized counseling might help pregnant people choose between elective induction at or beyond term or continuing to wait for labor. They stress that providers should honor the values and preferences of the mothers.
We need more research to know who would or would not benefit from elective induction. And the optimal time for induction is still not clear from the research, which is what they said in 2018. I think Rebecca’s going to talk about the famous Hannah post-term study that accounted for 75% of the data in that meta-analysis.
Yeah, so we’re kind of working backwards through time. We started with the 2019 randomized trials, then the 2018 meta-analysis where they said the optimal time for induction is not clear, but they stated that before the two new randomized trials came out. Then even before then going back in time is the 1992 Hannah post-term study, which is one of the most important studies on inducing for going past your due date and it was the largest randomized trial ever done on this topic, larger even than INDEX or SWEPIS. And it controls most of the findings in that Cochrane meta-analysis that Anna just described.
So let’s look at what happened in this study because it plays so much of a role in the meta-analysis. It was carried out between the years 1985 and 1990 when a group of researchers enrolled 3,407 low-risk pregnant people from six different hospitals in Canada into the study. Women could be included if they were pregnant with a live single fetus, and they were excluded if they were already dilating, if they had a prior cesarean, pre-labor rupture membranes, or a medical reason for induction.
This study had a much different expectant management protocol than INDEX or SWEPIS because unlike those studies where the longest you would go was 42 weeks and zero to one or two days, in the Hannah post-term study, the people assigned expectant management were monitored for as long as 44 weeks pregnancy before they were induced, so up to a month past your due date, which is almost unheard of today. At around 41 weeks, people who agreed to be in the study were either randomly assigned to have an induction of labor or fetal monitoring with expectant management.
In the induction group, labor was induced within four days of entering the study, usually about 41 weeks and four days. If the cervix was not ripe and if the fetal heart rate was normal, they were given a prostaglandin E2 gel to ripen the cervix. They used a maximum of three doses of gel every six hours. If this did not induce labor or if they did not need the gel, people were given IV oxytocin, had their waters broken, or both. And they could not receive oxytocin until at least 12 hours after the last prostaglandin dose.
So one strength of this study is that it had a defined induction protocol that providers could replicate. But the big weakness of this study is that the expectant management group did not have that same induction protocol. In the monitored or expected management group, people were taught how to do kick counts every day and they had a non-stress tests three times per week. They also had their amniotic fluid levels checked by ultrasound two to three times per week. And labor was induced if there were concerning results in the non-stress test, or if there was low amniotic fluid, or if the mother developed complications, or if the person did not go into labor on their own by 44 weeks. And if doctors decided the baby needed to be born, mothers in expectant management group did not receive any cervical ripening. Instead, they either had their water broken and/or IV oxytocin, or they just went straight to a cesarean without labor. So Anna, do you want to talk a little bit about what the researchers found in the study?
Anna Bertone: What the researchers found in the Hannah post-term study is that in the induction group, 66% of the people were induced and 34% went into labor on their own before induction. And in the expectant management group, 33% were induced and 67% went into labor on their own. There were two stillbirths in the group assigned to wait for labor and zero in the group assigned to induction. This difference was not considered to be statistically significant, which means we don’t know if it happened by chance or if it was a true difference between the groups. The more interesting outcome to look at with the Hannah post-term trial are the findings on cesarean rates because they differ depending on what numbers you look at. You can either look at the outcomes for the two original groups, which were the people randomly assigned to induction and then those assigned to expectant management, or you can look at the breakdown of what actually happened to the people in the two groups, in other words what happened to the people who were actually induced or who actually went into spontaneous labor.
Anna Bertone: So what happened in the original randomly assigned groups? If you look at the two original groups, the overall cesarean rate was lower in the induction group. It was 21.2% versus 24.5%. That was even after taking into account factors like the mother’s age, whether or not it was her first baby, and cervical dilation at the time of study entry. Or you could look at what happened with the people who were actually induced or who actually went into labor on their own. And if you look at that, you see two very interesting things. You see that people who went into spontaneous labor, regardless of which group they were assigned to, they had a cesarean rate of only 25.7%. But if people in the monitoring group had an induction, their cesarean rate was much higher than all the other groups. It was 42%. The same was true for both first-time mothers and for mothers who had given birth before.
Anna Bertone: So what does this mean? It means that only the people who were expectantly managed but then had an induction had a really high cesarean rate. The people who were expectantly managed and then went into labor spontaneously did not have a higher cesarean rate. One possible reason for this, for the highest cesarean rate seen in the people who were assigned to expectant management but then ended up getting an induction, is that the people in this group might’ve been higher risk to begin with since a medical complication could have led to their induction. The people that were assigned to expectant management and never developed a complication requiring an induction, those were the lower risk people, which means they were the ones less likely to end up giving birth by cesarean.
Anna Bertone: Then, another important factor that I know Rebecca has discussed previously is that doctors might’ve been quicker to call for a cesarean when assisting the labors of people with medical inductions if their pregnancies were beyond 42 weeks. They may have been less patient waiting for labor.
…Or more easily worried about the course of the labor, big baby, etc. –
Anna Bertone: Yes. More worried.
So basically, it seems like from the Hannah post-term trial, one of the benefits of considering expectant management is that if you do have spontaneous labor, your chance of cesarean is pretty low. But the risk is that you’ll develop medical complications and need an induction, in which case an induction at 42 weeks is going to be riskier than an induction at 41 weeks. So what do you think? We have all this research from all over the world, from the Hannah post-term trial, to the 2018 meta-analysis, to two trials out in 2019. Do you still feel like routine induction at 41 weeks is still going to be controversial or not?
Anna Bertone: I think it’s definitely still controversial, and I think everybody’s still processing the results from the INDEX trial and the SWEPIS trial. Rebecca and I reached out to Dr. Wennerholm who conducted the SWEPIS trial in Sweden, and she said she’s currently working on secondary analysis of the data. They’re talking about the economic implications of the findings in Sweden and what it means for Swedish national policy. So I think it’s still controversial. People are still talking about what to make of these findings.
Anna Bertone: There was another systematic review from 2019 by Riedel. This one came out too early to include the SWEPIS and the INDEX trials, but it’s still interesting to look at. Because unlike the Middleton Cochrane review, these authors were specifically interested in induction during the 41st week of pregnancy versus during the 42nd week of pregnancy. So in their analysis, they restricted the studies only to people having a routine induction at 41 weeks and zero to six days versus routine induction at 42 weeks and zero to six days. If you remember, the Cochrane review was much broader than that. They also only looked at studies published within the last 20 years. They only looked at studies with low-risk participants, and they ended up with three observational studies, two randomized controlled trials, and two studies that they called “quasi experimental studies”, which they grouped with the randomized controlled trials even though these studies weren’t truly randomized.
Anna Bertone: What they found was one perinatal death in the 41 week induction group and six deaths in the 42 week induction group. That was a rate of 0.4 versus 2.4 per 1,000. This finding was not statistically significant. In other words, we don’t have strong enough evidence that this couldn’t have happened by chance. These same studies, those two randomized controlled trials and the two quasi experimental studies, they showed no difference in cesarean rates between groups also. But the authors did report that one observational study found an increase in the cesarean rate with the 41 week induction group. So basically, they’re saying if you look much more narrowly at the evidence of induction during the 41st week versus the 42nd week, then there might not be a significant difference in the death rate.
But that Riedel study from 2019 is already outdated because that was before the two big randomized trials came out.
Anna Bertone: Yes. We need to see a systematic review and meta-analysis that includes those two randomized controlled trials and see if that changes. These authors also expressed concerns about the cesarean rate possibly rising with 41-week induction because both the SWEPIS trial and the INDEX trial took place in countries with very low cesarean rates. So we just don’t really know at this point whether there would be a difference in cesarean rates if they took place in countries with higher rates of cesarean, such as the U.S.
Anna Bertone: So I think it is still controversial. There’s also countries that are changing their policies about induction and going back and looking at whether that policy change led to any difference in outcomes. One such country is Denmark. They just published a study where they compared birth outcomes from 2000 to 2010 versus 2012 to 2016. And in that time period there was a change in policy from recommending induction at 42 weeks and zero days to 41 weeks and three to five days. They included over 150,000 births in the dataset. And when they looked back, they didn’t see any difference in stillbirths, or perinatal deaths, or low Apgar scores when they compared the period before versus after the policy change. The perinatal death rate was already declining before the policy change in 2011, and it just continued going down without any additional impact from the 2011 policy change. There was also no impact on the rate of Cesareans with the policy to switch from 42 weeks to 41 weeks.
Anna Bertone: That’s just an example of how this is still controversial. Countries are implementing new policies, and Sweden and the Netherlands may implement new policies based on the INDEX and the SWEPIS studies. Then they’ll probably conduct a study the same way that Denmark did to see if that policy change had any real impact on the population.
I think it’s important to mention, though, that with the Denmark national policy, they switched from 42 weeks and zero days to 41 weeks and three to five days, and that might not have been early enough to make an impact on the stillbirth rate because the studies that we were looking at from 2019, SWEPIS and INDEX, were looking at inductions happening at 41 weeks and zero to one or two days and it was that couple of days difference that made the difference between low stillbirth rate and a higher stillbirth rate.
Anna Bertone: Right. Exactly. I think that future researchers shouldn’t group 41 weeks and zero to six days together in one grouping because there seems to be differences between the earlier part of the 41st week and the later part of the 41st week because, like you said, SWEPIS and INDEX found that waiting even just two or three days make a difference in outcomes during that week.
So let’s just sum up the pros and cons of induction at 41 weeks versus continuing to wait for labor since that’s what we have the bulk of the evidence on now. I would say that the research shows that the pros of inducing labor at 41 weeks include a lower risk of stillbirth, especially among those with risk factors for stillbirths such as being pregnant with your first baby. In our article, we have a table of the pros and cons. The absolute risk of stillbirth is 4 out of 10,000 pregnancies at 39 weeks, 7 out of 10,000 pregnancies at 40 weeks, 17 out of 10,000 pregnancies at 41 weeks, and 32 stillbirths out of 10,000 pregnancies at 42 weeks. Research also shows a lower risk of the baby receiving intensive care with an elective induction at 41 weeks, lower risk of the baby having jaundice, lower risk of the baby being large for gestational age, and lower risk of needing a cesarean, although that finding may depend on your practice setting. There is a lower risk of mother developing a high blood pressure disorder. at the end of pregnancy. And for some people, they may find an elective induction at 41 weeks convenient and it could help them end an uncomfortable pregnancy.
Also, in our article, we reference one study that found some cognitive benefits for babies. It suggests that the cognitive benefits for the baby from the mom remaining pregnant appear to increase until about 40 to 41 weeks after which there’s no cognitive benefits to the baby’s brain development for continuing to remain pregnant. So Anna, can you share the cons of elective induction at 41 weeks?
Anna Bertone: Yeah. One of the cons of being induced at 41 weeks instead of continuing to wait and see if you go into labor is the potential for medicalization of birth. One example of this is continuous fetal monitoring may occur if you have the induction, whereas you might not get continuous fetal monitoring if you go into labor on your own spontaneously during that 41st week.
Anna Bertone: Another con would be a potential for failed induction leading to a cesarean. That also depends a lot on your practice setting. Another con is the potential for uterine tachysystole, which is defined as more than five contractions in 10 minutes averaged over 30-minute window. There’s a potential increase in the risk of uterine rupture with medical induction. That is especially important among people with a previous cesarean having a VBAC.
Anna Bertone: Another con is missing the hormonal benefits of spontaneous labor. Another con is increased risk of mother getting inflammation of the inner lining of the uterus, endometritis. One study found that as a possible risk of induction 41 weeks. Then, lastly, medically-induced contractions might increase pain and make epidural use more likely.
We also have a section in the article where we talk about whether there are any benefits to going past your due date. That table we just took you through was comparing the benefits and risks of elective induction. In terms of benefits of going past your due date, one of the major benefits of awaiting for spontaneous labor are the hormonal benefits, which Anna briefly mentioned. In our article, we link to the book Hormonal Physiology of Childbearing by Dr. Sarah Buckley, which talks about the physiologic understandings and the physiology of spontaneous labor. So that is something to keep in mind, and that’s one reason why some people prefer to wait for spontaneous labor. So Anna, if someone wants to wait for labor to begin on its own and they’re talking with their care provider about expectant management, what’s kind of the bottom line about that?
Anna Bertone: I think the bottom line about that is it all needs to be very individualized. When someone goes past their estimated due date, they could talk to their care provider about the benefits and the risks of elective induction versus continuing to wait for labor and how those benefits and risks apply to them personally. Most research articles and guidelines say that because there are benefits and risks to both options, the pregnant person’s values, goals, and preferences should play a part in the decision-making process.
Anna Bertone: It’s important for expectant families to be aware of the growing research evidence showing that there could be worse health outcomes for those who wait for labor after 41 weeks of pregnancy instead of being induced at 41 weeks, especially among first-time mothers and those with additional risk factors for stillbirth. But ultimately, after receiving accurate evidence-based information and having conversations with their care providers, pregnant people have the right to decide whether they prefer to induce labor or wait for spontaneous labor with appropriate fetal monitoring.
I want to also let people know about a couple more resources that are in this article at evidencebasedbirth.com/inducingduedates. We have a section all about how people and their care providers can talk about the risk of stillbirth with some sample scripts that healthcare providers can use when they’re talking about risks of stillbirth. We also have links to different guidelines from different organizations about induction at 41 weeks. Then we also have our section called The Bottom Line. So what would you say are some of the bottom lines, Anna, about elective induction at 41 weeks and zero to two days?
Anna Bertone: I think the bottom line is that elective induction at 41 weeks and zero to two days could help to reduce stillbirths and poor health outcomes for babies without increasing harm, like the risk of Cesarean for mothers. We’re getting that from those two large randomized controlled trials published in 2019 that both found benefits to elective induction at 41 weeks instead of continuing to wait for labor until 42 weeks. One of those studies, as we mentioned, found less perinatal death with 41 week induction and the other found fewer poor health outcomes for babies like intensive care unit admission and low Apgar scores with 41 week induction. Neither of those trials found an increase in the risk of Cesarean during birth with 41 induction compared to continuing to wait for labor until 42 weeks. However, both of those trials took place in countries that follow the midwifery model of care and the overall Cesarean rates were very low. So I think it remains to be seen how that will translate into countries like the U.S. that have higher Cesarean rates.
So I hope you all found this podcast helpful in looking at the recent research on induction at 41 weeks versus expectant management. Make sure you check out the blog article that goes along with this podcast episode for all of the resources, links, research references. We also have a free one-page handout you can download that summarizes the results of this research. Just go to evidencebasedbirth.com/inducingduedates to download that new article. Thank you so much, Anna, for joining us to help our listeners understand the evidence.
Anna Bertone: Happy to do it, Rebecca. Thank you.
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