EBB 153 – Pros and Cons of the Foley and Dilapan-S® for Cervical Ripening During an Induction

References on Cervical Ripening:

• Curran, M. (2020). Bishop Score Calculator. Click here.
• Kolkman, D. G. E., Verhoeven, C. J. M., Brinkhorst, S. J., et al. (2013). Bishop score as a predictor of labor induction success: a systematic review. American Journal of Perinatology, 30(8), 625-30. Click here.
• Ivars, J., Garabedian, C., Devos, P., et al. (2016). Simplified Bishop score including parity predicts successful induction of labor. Eur J Obstet Gynecol Reprod Biol., 203, 309-314. Click here.

References on the Foley:

• Abdelhakim, A. M. Shareef, M .A., AlAmodi, A. A., et al. (2020). Outpatient versus inpatient balloon catheter insertion for labor induction: A systematic review and meta-analysis of randomized controlled trials. Journal of Gynecology Obstetrics and Human Reproduction, In Press. Click here.
• Alfirevic, Z., Keeney, E., Dowswell, T., et al. (2016). Methods to induce labour: a systematic review, network meta-analysis and cost-effectiveness analysis. BJOG., 123(9), 1462-1470. Click here.
• American College of Obstetricians and Gynecologists (2009, Reaffirmed 2019). ACOG Practice Bulletin No. 107: Induction of labor. Obstet Gynecol.,114(2 Pt 1), 386-397. Click here.
• de Vaan, M. D. T., ten Eikelder, M. L. G., Jozwiak, M., et al. (2019). Mechanical methods for induction of labour.
Cochrane Database of Systematic Reviews 2019, Issue 10. Art. No.: CD001233. Click here.
• Dong, S., Khan, M., Hashimi, F., et al. (2020). Inpatient versus outpatient induction of labour: a systematic review and meta-analysis. BMC pregnancy and childbirth, 20(1), 382. Click here.
• Leduc, D., Biringer, A., Lee, L., et al. (2013). Induction of Labor: SOGC Clinical Practice Guideline. No. 296, 35(9), 840-857. Click here.
• Liu, X., Wang, Y., Zhang, F., et al. (2019). Double- versus single-balloon catheters for labour induction and cervical ripening: a meta-analysis. BMC pregnancy and childbirth, 19(1), 358. Click here.
• Simpson, K. R. (2020). Cervical Ripening and Labor Induction and Augmentation, 5th Edition. AWHONN Practice Monograph, 24(4), PS1-S41. Click here.

References on Dilapan-S:

• American College of Obstetricians and Gynecologists (2009, Reaffirmed 2019). ACOG Practice Bulletin No. 107: Induction of labor. Obstet Gynecol.,114(2 Pt 1), 386-397. Click here.
• Levine, L. D., Valencia, C. M. and Tolosa, J. E. (2020). Induction of labor in continuing pregnancies. Best Pract Res Clin Obstet Gynaecol., S1521-6934(20), 30079-1. Click here.
• Gupta, J., Chodankar, R., Baev, O., et al. (2018). Synthetic osmotic dilators in the induction of labour-An international multicentre observational study. Eur J Obstet Gynecol Reprod Biol., 229, 70-75. Click here.
• Saad, A. F., Villarreal, J., Eid, J., et al. (2019). A randomized controlled trial of Dilapan-S vs Foley balloon for preinduction cervical ripening (DILAFOL trial). Am J Obstet Gynecol., 220(3), 275.e1-275.e9. Click here.

Hi, everyone. On today’s episode, we’re going to talk about the options of using Dilapan-S® and the Foley for cervical ripening during a medical labor induction.

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, and welcome to today’s episode of the Evidence Based Birth® Podcast. Today we’re going to talk about cervical ripening, the Bishop score, and some mechanical ways to ripen the cervix. This episode is going to wrap up the series we’ve been doing this year. We started talking about natural induction methods, focusing on one new method per month on the podcast. And then two episodes ago, in episode 151, we talked about membrane stripping, which actually is a mechanical method of cervical ripening, and we’re going to expand on that topic in this podcast.

Whenever you have a formal medical labor induction, it usually involves two steps. First, cervical ripening is done to physically soften and eventually thin and dilate the cervix in preparation for labor and vaginal birth. Second, when the cervix is favorable, labor induction stimulates uterine contractions artificially to promote the start of labor. Clinicians often use the Bishop score to determine if cervical ripening is beneficial before an induction.

The Bishop score is based on results from a vaginal exam that uses five measurements to determine the readiness of the cervix for labor, which sometimes people call cervical ripeness. Cervical dilation is the measure of how dilated or open the cervix is in centimeters. You can get anywhere from zero to three points for the dilation of your cervix. Cervical effacement is the percentage of how effaced or thin the cervix is. Zero percent means the cervix is normal pre-labor, and 100% effaced means the cervix is paper-thin, and very ready to go into labor. Again, just like with dilation, with the Bishop score, you get anywhere from zero to three points for cervical effacement.

Next, fetal station is a measure of how far the fetal head has descended into the birth canal. Negative numbers mean the baby is floating above the pelvis. Zero station means the baby is fully engaged in the pelvis. And positive numbers mean the baby is crowning and beginning to emerge from the birth canal. Again, you can get anywhere from zero to three points for fetal station.

Next, cervical position refers to the position of the cervix relative to the pelvis and the fetal head. When it is favorable for labor, the cervical position changes from posterior, toward the back, to interior, toward the front. And you can get anywhere from zero to two points for the position of the cervix. Finally, you measure cervical consistency, how the cervix feels. A firm cervix feels like the tip of the nose, and a soft ripened cervix feels more like the lips. You can get anywhere from zero to two points for the consistency of the cervix.

All of these sub-scores are added up to get the total Bishop score. If the total Bishop score is higher than eight, then the chance of having a vaginal birth with a medical labor induction is very good. Similar to the chance of having a vaginal birth after a labor that starts on its own, or spontaneously. A score of six or less means that the cervix is unfavorable for induction, and that cervical ripening methods should be considered to increase the chance of having a vaginal birth with your induction.

A Bishop score of seven is not clearly favorable or unfavorable for induction. We reviewed the research on this subject, and we found many studies that show that higher Bishop scores are linked to a higher chance of vaginal birth with induction, and lower scores are linked to a higher chance of cesarean if you have an induction. However, the Bishop score is still not considered a super-great predictor of success or having a vaginal birth with an induction, especially if you have a middle-range score, a four, five, or six. There is something called a simplified Bishop score. The simplified Bishop score uses only dilation, effacement, and station, and research shows that it appears to be as good as the original Bishop score at predicting a vaginal birth with induction. Using these three components, a score of more than five is considered favorable for induction.

A major limitation of the Bishop score is that it does not consider whether someone has given birth before. And having a prior vaginal birth has been found to be a very important factor, perhaps the most important factor, in predicting whether or not an induction will be successful. Some researchers have proposed modifying the Bishop score to add points for people who have already had at least one vaginal birth in the past. However, despite its limitations, the Bishop score is still useful in helping to decide whether cervical ripening is beneficial before induction.

If you want to calculate your own Bishop score, it can be helpful to ask your provider at your appointment, if you choose to accept a vaginal exam, what your Bishop score is as you’re nearing term, especially if your provider is recommending an induction. It’s always a good idea to ask, “What’s my Bishop score?” If your Bishop score is low, you will likely need cervical ripening before you have an induction. You can also look up Bishop score calculators online. Just google, “Bishop score calculator,” and any number of versions will pop up, and they’re all virtually the same.

So, many people, before they go in for an induction, or when they arrive for an induction, do have to undergo medical cervical ripening first. Medical cervical ripening methods can be divided into mechanical and pharmacologic, or drug-based methods. They can be used alone, or in combination. And for the rest of this podcast, we’re going to focus solely on mechanical methods of cervical ripening.

I did want to let you know that, in a few weeks, we are releasing a brand new pocket guide all about the evidence on labor induction. We’re going to cover all of the evidence on the reasons for labor induction, the medical and mechanical and pharmacological ways of inducing labor, as well as natural methods of inducing labor. So in this podcast, I’m focusing just on the mechanical methods, but we do cover the medications that are used to ripen the cervix, and induce labor, in our new pocket guide. If you want to get on the list for the pocket guide, the waitlist, just go to evidencebasedbirth.com/waitlist. We will be doing a limited printing run of our pocket guides at the end of November, so make sure you’re on the waitlist if you want to get your hands on one of the pocket guides.

All right. So, mechanical methods of cervical ripening. Mechanical methods are drug-free methods that involve the use of hands or medical devices to promote labor. A few weeks ago, in episode 151, we talked about membrane sweeping, which is also referred to as membrane stripping, or the stretch and sweep of the membranes. That involves inserting one or two gloved fingers into the vagina, and through the cervix, and then using a continuous circular sweeping motion to gently separate the bag of water that surrounds the baby from the lower part of the uterus.

This procedure is done to increase your body’s natural release of hormones that contribute to cervical ripening. And we covered all of the evidence on the pros and cons of membrane sweeping in episode 151. So, I won’t go over any more in this episode. Another mechanical method to ripen the cervix is something called cervical osmotic dilators, and these are thin rods that are inserted into the vagina and through the opening of the cervix. To use cervical osmotic dilators, the cervix must be at least partially dilated about one centimeter at least.

Usually several rods are inserted together. The rods absorb water from the surrounding tissue, which causes them to gradually swell and stretch the cervix. Laminaria is made from sterile, dried seaweed, and Dilapan is made from a synthetic gel material. Laminaria has been used in the United States since 1869, but was withdrawn from the market because of increased risk of infection. It was reintroduced in the 1970s, when new sterilization techniques became available to make the laminaria rods sterile. But it was largely replaced by synthetic Dilapan dilators in the early 1980s. The synthetic dilators have the advantage of assured sterility, a softer and more uniform shape, superior dilating properties, and they avoid the risk of allergic reaction that can occur with laminaria.

The U.S. FDA approved the use of something called Dilapan-S®, S stands for super version, in 2015 for cervical ripening. The new version was made with stronger material than the original Dilapan. Dilapan-S® has been on the market for 21 years, and is used in 41 countries, and it can be used both outpatient and inpatient. Another method of mechanical cervical ripening is using a balloon catheter. Balloon catheters are actually the most common form of mechanical cervical ripening when you go in for a formal medical induction.

The single balloon catheter, called a Foley catheter, F-O-L-E-Y, is a small, sterile, rubber tubing that is inserted into the vagina and through the opening of the cervix. To use this method, the cervix must be at least partially dilated, at least one centimeter dilated. After the sterile tubing is passed through the opening of the cervix into the uterus, a single balloon is inflated with sterile fluid, causing the balloon to press down gently on the cervix from the inside, and causing a physical stretching of the cervix. The pressure of the balloon on top of the cervix also stimulates the release of natural hormones that promote cervical ripening.

The catheter can be taped to the pregnant person’s leg so that it is kept under tension. Research has found potential benefits to the outpatient use of Foley balloon catheters. You might also be interested to know that there is also a double-balloon catheter called the Cook, or a TAD catheter. But researchers have found that the double-balloon catheter is no more effective than the single-balloon Foley catheter, and the double-balloon catheter reportedly causes people more discomfort. The U.S. FDA has approved the double-balloon catheter for labor induction, while the single-balloon catheter is used off label.

Another mechanical method that I’m not really going to go into is amniotomy, which is the artificial rupture of membranes, also called artificially breaking the water. Breaking the water could, theoretically, help ripen the cervix because it’s linked to the release of chemicals and hormones that stimulate contractions. But more often, it’s actually used in trying to induce labor with contractions, not necessarily to ripen the cervix. So, we won’t cover amniotomy in this episode. However, it is covered in the pocket guide on labor induction.

At this point, though, you might be wondering, “Why would we even want to use mechanical methods of cervical ripening if there are medications available?” And there are several medications on the market that can be used to ripen the cervix. I cover those medication methods in detail in the pocket guide on induction that we’re releasing soon. Well, the reason mechanical methods are so quite popular is because they are a drug-free method. They involve the use of hands or medical devices, but because you’re not giving someone a systemic medication, they have less risk of something called hyperstimulation.

Hyperstimulation of the uterus is a broad term that includes something called tachysystole, which is when you have more than five contractions in ten minutes, averaged over 30 minutes. Tachysystole and excessive uterine activity can lower oxygen levels to the fetus and lead to fetal distress. So, because mechanical methods have a much lower risk of hyperstimulation, they tend to be pretty popular methods for ripening the cervix. Of course the problem is, with the laminaria, the Dilapan-S®, and the Foley bulb catheter, you really need to be about one centimeter dilated before any of those methods can be used to ripen the cervix. So, they might not be available to everyone.

So, now I want to take you deeper into the evidence on two of these topics. The cervical osmotic dilators, and the Foley catheter. So, let’s talk about the cervical osmotic dilators, and in general, when I’m talking about those, I’m going to be talking about the Dilapan-S®, which are those sterile rods that you put in the cervix that swell and help dilate the cervix. The information we have on the effectiveness of cervical osmotic dilators comes from a randomized trial, as well as a prospective multicenter study.

In the randomized trial on Dilapan-S®, there were 419 U.S. participants who had either Dilapan-S® or the Foley balloon for cervical ripening. To be in the study, everyone was at least 37 weeks pregnant, and scheduled for an induction with an unripe cervix. People were excluded from the randomized trial if they had ruptured membranes, infection, a prior uterine scar, vaginal bleeding, a suspected big baby, or if they required immediate delivery. The study included both first-time mothers and experienced mothers. Everyone received continuous monitoring for 20 minutes before the device was placed, either the Dilapan-S® or the Foley.

As many Dilapan-S® rods as would fit were placed in the cervical canal, and those who had a Foley balloon had it inflated with 60 milliliters of saline. Study participants remained at the hospital, but were able to walk around, shower, and perform normal activities. If the assigned dilator was still in place after 12 hours and the cervix remained unripe, then the dilator was used for another round of 12 hours.

The researchers found a trend towards more vaginal birth with Dilapan-S® compared to the Foley balloon, 81% versus 76%. But this difference was not large enough to conclude definitively that Dilapan-S® is a better option than Foley. However, the study authors did say that Dilapan-S® is at least an equally good option, and the safety outcomes during cervical ripening were similar for people who had either Dilapan-S® or Foley, and there were no differences in other birth outcomes between the groups.

Even though the divide remained in place longer on average, the pregnant people assigned to Dilapan-S® reported that they were significantly more satisfied than those assigned to Foley, as far as sleep, their ability to relax, and their ability to perform daily activities. Next, a prospective multicenter study analyzed data from 444 participants in seven countries who used synthetic osmotic dilators for labor induction. Everyone was between 37 and 42 weeks of pregnancy, and about 65% were giving birth for the first time, and 35% had given birth before, including over nine percent of people with one prior cesarean.

The average baseline Bishop score was 2.9, and this increased to 6.5 after using Dilapan-S® for cervical ripening. Three to four dilator rods were used on average. The overall rate of vaginal birth after Dilapan-S® was 70%, however, the vaginal birth rate was higher, 77%, among the 188 participants who used the device for less than 12 hours. Only about ten percent of people went into labor on their own after cervical ripening with Dilapan-S®. In other words, most people had to use other methods of induction after they concluded cervical ripening with Dilapan-S®. So, the device is not used to avoid an induction, but rather to improve the chance of vaginal birth with an induction.

The authors found Dilapan-S® to be safe and effective for cervical ripening, including among people with prior cesareans. There were no bad newborn outcomes from the use of Dilapan-S®. A few people experienced complications from the device, such as bleeding during insertion or removal, 2.7%, and cramping or pain, 0.2%. And there were no infections linked to the use of Dilapan-S®. So, to sum up the advantages and disadvantages of Dilapan-S®, the advantages are that this is a drug-free method of cervical ripening that has a similar effectiveness to the Foley balloon. Unlike medications, Dilapan-S® does not cause systemic or whole-body side effects, and it’s less likely to cause strong uterine contractions while the cervix is ripening.

It’s not contraindicated for people with a prior caesarian. If you’d had a caesarian in the past, there’s a lot of medication methods that might not be appropriate options for you because of the increased risk of uterine rupture. So, it is something that somebody with a prior caesarian could use for cervical ripening. It’s also well suited to the outpatient setting, or in countries or locations with limited access to fetal monitoring. Once you have the rods inserted, it’s possible to use the toilet, shower, walk around, sleep, and perform activities as normal.

It can be removed, so there’s a potential for reversibility if you changed your mind about using it, and some pregnant people have reported higher satisfaction levels with Dilapan-S® compared to using the Foley. Also, unlike the Foley balloon, Dilapan-S® does not protrude from the vagina. It remains mostly in the cervical canal. So, there’s no need to have something taped to your leg.

The disadvantages of Dilapan-S® are that it’s not commonly used in many birth settings. So, providers might not be familiar with this alternative to the Foley for mechanical cervical ripening. The procedure requires a vaginal exam to assess cervical ripeness, and a period of in-person monitoring before and after device placement. You may go on to still require medications to ripen the cervix if the cervix is not dilated enough to insert the rods. You may have pain or discomfort with the procedure, and there is a low risk of potential bleeding from inserting or extracting the rods.

Dilapan-S® has not been well studied among people with ruptured membranes, so if your water’s already broken, there isn’t research, really, on that. And it cannot be used if there is a low lying placenta or any kind of infection in the genital tract. In terms of practice guidelines and what they have to say about Dilapan-S®, Dilapan-S® is not specifically mentioned in practice guidelines for induction. However, in the United States, ACOG recommends, in general, osmotic dilators as effective in ripening the cervix for labor.

In preparing to record this podcast and create our pocket guide on induction, Aniber Tony from our research team attended an interesting seminar on Dilapan-S® taught by Dr. Saad, S-A-A-D, the lead United States researcher on this topic. It’s a great opportunity to ask questions and learn more, especially if you’re a healthcare provider in this area and you want to learn more about cervical osmotic dilators.

So, if you want to register for an upcoming seminar, I will put in the show notes the email address of the person that you can email to ask about seminars with Dr. Saad. So now, let’s talk about the balloon catheters and their effectiveness for ripening the cervix. When we look at the research on the effectiveness of balloon catheters, most studies used a 16 to 20 french Foley catheter, and inflate it with anywhere from 30 to 80 milliliters of sterile fluid. When randomized trials have been combined into a meta-analysis, researchers have found a shorter time to birth by about two hours, with an increased inflation volume of 60 milliliters versus 30 milliliters.

Interestingly, there’s no evidence of benefit from using a double-balloon over a single/Foley balloon, and the single-balloon is reported to be safer and less painful, even though it’s the double-balloon that is FDA approved. In looking at the research on the Foley balloon, which is the single-balloon, compared with placebo, a sham treatment, the Foley catheter improved the odds of a vaginal birth within 24 hours and lowered the risk of cesarean. Compared with a medication called Dinoprostone, which is inserted vaginally, the balloon catheter was just as effective as the medication at resulting in vaginal birth within 24 hours, and there was no difference in the risk of cesarean.

Compared to the medication Dinoprostone, the balloon catheter is safer for babies on a number of outcomes, including uterine tachysystole, or hypersystole, which is a contraction that lasts at least two minutes with fetal heart rate changes. The balloon catheter was also safer in terms of lower rates of cesareans for fetal distress and serious newborn health complications or death.

Pregnant people who were randomly assigned to the balloon were more satisfied with their birth experience compared to those who were assigned to the medication of vaginal Dinoprostone. Researchers think that the benefits of the Foley balloon over vaginal Dinoprostone are so clear that no more research on this comparison is necessary. The Foley balloon is better than Dinoprostone, the medication, hands down. When the researchers compared the Foley balloon to intracervical Dinoprostone, the balloon led to less fetal distress with no difference in effectiveness. Compared to a different medication called low dose vaginal misoprostol, the balloon might not be quite as effective because there was a lower risk of cesarean with a low dose vaginal misoprostol.

However, the balloon was safer for the baby, lowering the risk of uterine tachysystole or hypersystole with fetal heart rate changes, as well as lowering the risk of meconium stained fluid. Compared to low dose oral misoprostol, where the medication misoprostol is taken by mouth, the balloon may be slightly less effective, as there was a lower rate of vaginal birth within 24 hours with the balloon. There’s not enough research yet to know if the balloon has better outcomes than oral misoprostol low dose in terms of uterine tachysystole, hypersystole, serious complications, or death.

In some research studies, pregnant people have reported higher satisfaction with oral misoprostol compared to the balloon. Two recent meta-analyses of randomized trials have compared outpatient to inpatient use of the balloon catheter, and found that outpatient use is safe and effective. Compared to having to be hospitalized, people who had the Foley balloon outpatient had significantly lower cesarean rates, a shorter length of hospital stay, and a more favorable increase in Bishop score.

With the outpatient use, there was a shorter time from placing the balloon catheter to birth, over five hours shorter on average, compared to people who were inpatients and were hospitalized for the procedure. Studies have not found an increased risk of infection when the balloon catheter is used among people with in-tact membranes, meaning your water has not broken yet. However, recent evidence suggests a possible increased risk of maternal infection when the Foley is used among people who have already had their water broken, or have ruptured membranes.

So, to sum up the advantages and disadvantages of the Foley balloon, the advantages are that it increases the rate of vaginal birth within 24 hours, compared to sham treatment, and it has similar effectiveness in terms of cervical ripening as the medication Dinoprostone. However, there is a lower risk of uterine hyperstimulation, which can lead to fetal distress, compared to using synthetic prostaglandins. So, the Foley balloon is safer for the baby than using medications.

Unlike medications, the balloon catheter does not cause systemic side effects, and it’s less likely to cause strong uterine contractions while the cervix is ripening. So far, it’s not been contraindicated for people with a prior caesarian. So, it is an option for cervical ripening for someone who’s had a prior caesarian. It’s also well suited to the outpatient setting, or in countries with limited access to fetal monitoring. Once you have the Foley inserted, it’s possible to use the toilet, shower, walk around, or sleep, although there may be a tube coming out of the vagina that is taped to the thigh for tension.

The Foley can be removed, so there’s the potential for reversibility if you change your mind. It’s widely available and relatively simple to use, and it’s stable at room temperature, and low cost. The disadvantages of the Foley are that it may be less effective than the medication misoprostol, and it’s less effective alone versus combined with other methods of induction. The procedure requires a vaginal exam to assess cervical ripeness, and a period of in-person monitoring before and after device placement.

If you are not around one centimeter dilated when it’s inserted, you might need to have medications to ripen your cervix first. Some people complain of pain or discomfort with the insertion procedure, and some people may have bleeding after the procedure. There also may be an increased risk of maternal infection if it’s used in someone who has ruptured membranes. And the Foley should not be used when there’s a low lying placenta or a genital tract infection.

In looking at the practice guidelines for the United States and Canada, in the United States, ACOG states that the Foley catheter is a reasonable and effective alternative for cervical ripening, and inducing labor, based on good and consistent scientific evidence. In Canada, the Society of Obstetricians and Gynecologists of Canada recommends Foley catheters as acceptable and safe, including for use with vaginal birth after cesarean, and in the outpatient setting.

So, that concludes the info on this podcast episode all about mechanical methods for ripening the cervix. I hope you found this information helpful. It was super interesting for our research team to look at the research on these methods, because they’re not really something we’ve ever covered before at the Evidence Based Birth® blog or podcast. In summary, we’ve covered the concept of cervical ripening, the Bishop score, and the mechanical methods of cervical osmotic dilators, including Dilapan-S®, and using the Foley balloon for cervical ripening.

Mechanical methods do have advantages over medication methods in that they’re less likely to cause hyperstimulation of the uterus, or tachysystole. However, there are some situations where the mechanical methods cannot be used, such as if you have a completely closed cervix. If you want to learn more about the medication methods of cervical ripening, I’d encourage you to get on the waitlist for our pocket guide. Just go to evidencebasedbirth.com/waitlist to be among the first to find out when the pocket guide is available for order.

Thanks, everyone. I hope you have a great rest of your week, and we’ll see you next time. Bye.

Today’s podcast was brought to you by the Signature Articles at Evidence Based Birth®. Did you know that we have more than 20 peer-reviewed articles summarizing the evidence on childbirth topics available for free at evidencebasedbirth.com? It takes six to nine months on average for our research team to write an article from start to finish, and we then make those articles freely available to the public on our blog. Check out our topics ranging from advanced maternal age, to circumcision, due dates, big babies, pitocin, vitamin K, and more.

Our mission is to get research evidence on childbirth into the hands of families and communities around the world. Just go to evidencebasedbirth.com, click on blog, and click on the filter to look at just the EBB Signature Articles.