Today on Evidence Based Birth, occasional contributor Rebecca Dekker, Phd, RN, APRN, provides a comprehensive research review – Induction for Going Past your Due Date: What does the Evidence Say? I had an opportunity to preview the article and ask Rebecca some questions about her most recent project on due dates. I would like to share our conversation here on Science & Sensibility with all of you. Rebecca's website has become a very useful tool for both professionals and consumers to read about current best practice.Consumers can gather information on the common issues that they maybe dealing with during their pregnancies. Professionals can find resources and information to share with students and clients. How do you cover the topic of inductions at term for due date? After reading today's S&S post and Rebecca's research post, do you think you might share additional information or change what you discuss? Let us know in the comments section.- Sharon Muza, Community Manager, Science & Sensibility.
Note: if the Evidence Based Birth post is not up yet, try again in a bit, it should be momentarily.
Sharon Muza: Why did you decide to tackle the topic of due dates as your next research project and blog post?
Rebecca Dekker: Last year, I polled my audience as to what they would like me to write about next. They overwhelmingly said that they wanted an Evidence Based Birth article about Advanced Maternal Age (AMA), or pregnancy over the age of 35. As I started reviewing the research on AMA, it became abundantly clear to me that I had to first publish an article all about the evidence on due dates. This article on induction for due dates creates a solid foundation on which my readers can learn about induction versus waiting for spontaneous labor in pregnant women who are over the age of 35.
SM: When you started to dig into the research, were there any findings that surprised you, or that you didn’t expect?
RD: There were two topics that I really had to dig into in order to thoroughly understand.
The first is the topic on stillbirth rates. I began to understand that it’s really important to know which mathematical formula researchers used to calculate stillbirth rates by gestational age. It was interesting to read through the old research studies and letters to the editors where researchers argued about which math formulas were best. In the end, I had to draw up diagrams of the different formulas (you can see those diagrams in the article) for the formulas to make sense in my head, and once I did, the issue made perfect sense!
Before 1987 (and even after 1987, in some cases) researchers really DID use the wrong formulas, and it’s kind of funny to think that for so many years, they used the wrong math! In general, I thought the research studies on stillbirth rates by gestational age were really interesting...it raised questions for me that I couldn’t answer, like why are the stillbirth rates so different at different times and in different countries? Also, it was really clear from the research that stillbirth rates are drastically different depending on whether you are looking at samples that include or don’t include babies who are growth-restricted.
The other big breakthrough or “ah ha” moment I had was when I finally realized the true meaning of the Hannah (1992) Post-Term study. There was such a huge paradox in their findings… why did they find that the expectant management group had HIGHER Cesarean rates, when clinicians instinctively know that inductions have higher Cesarean rates compared to spontaneous labor? Since all of the meta-analyses rely heavily on the Hannah study, I knew I needed to figure this problem out.
There are a couple different theories in the literature as to why there were higher C-section rates in the expectant management group in Hannah’s study. One theory is that the induction group had Prostaglandins to ripen the cervix, while the expectant management group did not. However, in a secondary data analysis published by Hannah et al. in 1996, they found that this probably played just a minor role.
Another theory is that as women go further along in their pregnancy, physicians get more nervous about the risk of stillbirth, and so they may be quicker to recommend a Cesarean in a woman who is past 42 or 43 weeks, compared to one who is just at 41 weeks. This theory has been proposed by several different researchers in the literature, and there is probably some merit to it.
But in the end, I found out exactly why the C-section rates are higher in the expectant management group in the Hannah Post Term study (and thus in every meta-analysis that has ever been done on this topic). Don’t you want to know why? I finally found the evidence in Hannah’s 1996 article called “Putting the merits of a policy of induction of labor into perspective.” The data that I was looking for were not in the original Hannah study… they were in this commentary that was published several years later.
The reason that Cesarean rates were higher in the expectant management group in the Hannah study is because the women who were randomly assigned to wait for spontaneous labor, but actually ended up with inductions, had Cesarean rates that were nearly double of those among women who had spontaneous labor. Some of these inductions were medically indicated, and some of them were requested by the mother. In any case, this explains the paradox. It’s not spontaneous labor that leads to higher Cesarean rates with expectant management… the higher Cesarean rates come from women who wait for spontaneous labor but end up having inductions instead.
So the good news is that if you choose “expectant management” at 41-42 weeks (which is a term that I really dislike, because it implies that you’re “managing” women, but I digress), your chances of a Cesarean are pretty low if you go into spontaneous labor. But if you end up being one of the women who waits and then later on chooses to have an induction, or ends up with a medically indicated induction, then your chances of a Cesarean are much higher than if you had just had an elective induction at 41 weeks.
SM: What information do you recommend that childbirth educators share to help families make informed decisions about inductions and actions to take as a due date comes and then even goes, and they are still pregnant.
RD: First of all, I think it’s important for all of us to dispel the myth of the 40 week due date. There really is no such thing as a due date. There is a range of time in which most women will go into labor on their own. About half of women will go into labor by 40 weeks and 5 days if you’re a first-time mom (or 40 weeks and 3 days if you’ve given birth before), and the other half will go into labor after that.
The other thing that it is important for childbirth educators to do is to encourage families—early in pregnancy—to talk with their health care provider about when they recommend induction, and why.
There are some health care providers who believe strongly that induction at 39, 40, 41, or 42 weeks reduces the risk of stillbirth and other poor outcomes. There are parents who have the same preference. Then there are other health care providers who believe strongly that induction for going past your due date is a bad thing, and shouldn’t be attempted unless there are clear medical reasons for the induction. And there are parents who will tend to share that same preference. Either way, parents need accurate information about the benefits and risks of waiting versus elective induction at 41-42 weeks—because both are valid options.
But it’s probably best to avoid a mismatch between parents and providers. If parents believes strongly that they want to wait for spontaneous labor, and they understand the risks, but they have a care provider who believes strongly in elective induction at 41 weeks, then they will run into problems when they reach 41 or 42 weeks and their care provider disagrees with their decision.
Clearly, there are benefits to experiencing spontaneous labor and avoiding unnecessary interventions. But at the same time there is a rise in the relative risk of stillbirth starting at about 39 weeks, depending on which study you are looking at. However, the overall risk is still low up until 42 weeks. At 42 weeks, the risk of stillbirth rises to about 1 in 1,000 in babies who are not growth-restricted. The risk may be higher in some women who have additional risk factors for stillbirth. Women who experience post-term pregnancy (past 42 weeks) are more likely to experience infections and Cesareans, and their infants are more likely to experience meconium aspiration syndrome, NICU admissions, and low Apgar scores.
SM: Would you recommend that families have conversations about how their due date is being calculated, at the first prenatal with their health care providers. What should that conversation include?
RD: I would recommend asking these questions:
- What is the estimated date range that I might expect to give birth—not based on Naegele’s rule, but based on more current research about the average length of a pregnancy?
- Did you use my Last Menstrual Period or an early ultrasound to determine my baby’s gestational age?
- Has my due date been changed in my chart at any point in my pregnancy? If so, why?
SM: The concept of being “overdue” if still pregnant at the due date is firmly ingrained in our culture. What do you think needs to happen both socially and practically to change the way we think about the “due date?”
RD: We need to start telling everyone, “There is no such thing as a due date.” To help women deal with the social pressure they may experience at the end of pregnancy, I’ve created several Facebook profile photos that they can use as their Facebook profile when they get close to their traditional “due date.” To download those photos, visit www.evidendebasedbirth.com/duedates
SM: How available and widely used are first trimester ultrasounds? If first trimester ultrasounds were done as the standard of care in all pregnancies, would it result in more accurate due dates and better outcomes? Do you think there should be a shift to that method of EDD estimation?
RD: I think the option of having a first trimester ultrasound definitely needs to be part of the conversation between a woman and her care provider, especially because it has implications for the number of women who will be induced for “post-term.” I could not find any data on the percentage of women who have an ultrasound before 20 weeks, but in my geographic area it seems to be nearly 100%, anecdotally.
If your estimated due date is based on your LMP, you have a 10% chance of reaching the post-term period, but if it’s based on an early ultrasound, you only have a 3% chance of reaching 42 weeks.
One strange thing that I noted is that ACOG still prefers the LMP date over an early ultrasound date. They have specific guidelines in their practice bulletin about when you need to switch from the LMP date to an ultrasound date, but the default date is still the LMP. I found that rather odd, since research is very clear that ultrasound data is more accurate than the LMP, for a host of reasons!
Before I published the due dates article, I reached out to Tara Elrod, a Certified Direct Entry Midwife in Alaska, to get her expert feedback as a home birth midwife. She raised an excellent point:
"It is of significant interest to me as a licensed midwife practicing solely in the Out-of-Hospital setting that ultrasounds done in early pregnancy are more accurate than using LMP. If early ultrasound dating was achieved, it's thought that this would ultimately equate to less women being induced for post-term pregnancy. This is significant to midwives such as myself due to the scope-of-care regulation of not providing care beyond 42 weeks. While an initial- and perhaps arguably by some 'elective' ultrasound- may not be a popular choice in the midwife clientele population, a thoughtful risk versus benefit consideration should occur, as to assess the circumstance of "risking out" of care for suspected post-dates. [In my licensing state, my scope of care is limited to 37+0 weeks to 42+0 weeks, with the occasional patient reaching 42 weeks and therefore subsequently "risking out," necessitating a transfer of care.]” ~Tara Elrod, CDM
SM: What do you think the economic cost of inductions for due dates is? The social costs? What benefits might we see if we relied on a better system for determining due dates and when to take action based on being postdates?
RD: There are economic costs to both elective inductions and waiting for labor to start on its own. The Hannah Post-Term trial investigators actually published a paper that looked at the cost effectiveness of their intervention, and they found that induction was cheaper than expectant management. This was primarily because with expectant management, there were extra costs related to fetal monitoring (non stress tests, amniotic fluid measurements, etc.) and the increased number of Cesareans in the expectant management group.
But there are many unanswered questions about the cost-effectiveness of elective induction of labor versus waiting for labor to begin (with fetal monitoring), so I’m afraid I can’t make any definitive statements or projections about the economic and social costs of elective inductions. Here is a study that may be of interest to some with further information on this topic.
I do know that in a healthy, low-risk population, birth centers in the National Birth Center Study II provided excellent care at a very low cost with women who had spontaneous births all the way up to 42 weeks. I would love to see researchers analyze maternal and neonatal outcomes in women stratified by gestational age in the Perinatal Data Registry with the American Association of Birth Centers.
SM: I very much look forward to all your research posts and appreciate the work and effort you put into doing them. What is on your radar for your next piece?
RD: The next piece will be Advanced Maternal Age!! After that, I will probably be polling my audience to see what they want, but I’m interested in tackling some topics related to pain control (epidurals and nitrous oxide) or maybe episiotomies.
SM: Is there anything else that you want to share about this post or other topics?
RD: No, I would just like to give a big thank you to everyone who helped in some way or another on this article!! There was a great interdisciplinary team who helped ensure that the due dates article passed scrutiny—we had an obstetrician, family physician, nurse midwife, several PhD-prepared researchers, and a certified direct entry midwife all provide expert review before the article was published. I am so thankful to all of them.
Hannah, M. E., C. Huh, et al. (1996). "Postterm pregnancy: putting the merits of a policy of induction of labor into perspective." Birth 23(1): 13-19.
Hannah, M. E., W. J. Hannah, et al. (1992). "Induction of labor as compared with serial antenatal monitoring in post-term pregnancy. A randomized controlled trial. The Canadian Multicenter Post-term Pregnancy Trial Group." N Engl J Med 326(24): 1587-1592.