Routine Elective Induction at 39 Weeks: Is It a Good Idea?

Even before the COVID-19 pandemic, many obstetricians and some midwives had begun recommending routine elective induction, meaning no medical reason for inducing labor, at 39 weeks. With the onset of the pandemic, more practitioners are making that recommendation, and some are making routine induction a requirement. Is elective induction at 39 weeks—or any other time, for that matter—a good idea?

Pre-pandemic, if you had asked why, you would probably have been told that research has shown that labor induction doesn’t harm babies, decreases the odds of having a cesarean, and averts the possibility of something going wrong in the final weeks. Those beliefs bolster making induction a requirement now that scheduled deliveries have become a boon to harried staff and, moreover, they permit pre-admittance COVID-19 testing. But is it true?

I’m going to argue that it’s not. I’m going to make the case that the research isn’t what it’s cracked up to be, and there are good reasons for letting Mother Nature decide when labor should begin. I’ll finish up, as I usually do, with take-away tips and ideas for making practical use of the information I’ve just given you.

What’s Wrong with the Concept of Routine Induction?

To begin with, routine induction at 39 weeks is problematic on its face. It is the only circumstance where doctors recommend interfering in a healthy, physiologic process that is proceeding normally. Doctors don’t, for example, propose installing pacemakers in older people with healthy hearts on the offhand chance that they might develop a problem down the line. For one thing, you can’t improve on a natural process that is working properly; you can only disrupt it.⁵⁸ For another, every medical intervention has potential harms. Using them on healthy people means exposing them to those harms with no counterbalancing benefit.

These two principles apply to routine induction. Preparation for labor involves a complex set of hormonal interactions that prepare the baby for life in the outside world, orchestrate the birth process, help mother and baby cope with the stress of labor, promote successful breastfeeding, and foster attachment between mother and child.¹⁰ And the drugs and procedures used to induce labor come with risks, including, fortunately rarely, causing severe and life-threatening complications.

You may be wondering why obstetricians make childbirth the exception to the rule. Because most obstetricians, historically and up to the present day, have a strong bias favoring induction over waiting for labor to start on its own. This is for two reasons: One is self-interest: scheduling labor makes life easier,⁶⁴ which, with the pandemic, has become an even stronger motivation for obstetricians and hospital staff. The other is a deep distrust of the natural process, which leads to a belief that aggressive medical management will produce better outcomes.¹³ Propelled by their bias, obstetricians have spent decades trying to prove that induction is the way to go. For every problem the research turns up, they’ve tried to show that it’s not really a problem, or they have a solution that solves the problem, and they turn a blind eye to research that contradicts the results they want to see. The scientific name for this is confirmation bias: “The tendency to search for, interpret, favor, and recall information in a way that affirms one’s prior beliefs or hypotheses.”

With this perspective in mind, let’s look at the research.

Is Routine 39-Week Induction Warranted?

The last couple of decades of research have seen a push attempting to show either that induction doesn’t cause harms, such as increased cesareans or fetal distress, or that its harms can be eliminated with proper management. For example, the 39-week green light for induction was the obstetric community’s response to research showing that while 37 weeks is considered full term, inductions before 39 weeks resulted in an excess of babies with breathing difficulties at birth. Solution: wait until 39 weeks to induce. Problem solved; never mind the problems you may still be causing that aren’t quite as dramatic as a baby having trouble breathing.

In the past few years, that push has shifted from trying to show that induction is just as good as waiting for labor to trying to show that it’s better. (If you want an analysis of the research for and against routine induction, scroll down to “Taking a Deeper Dive.”) The trial that has led to recommending routine induction at 39 weeks is the culmination of that effort. Published in 2018, investigators randomly assigned 6100 healthy, 1^st-time mothers at 41 hospitals to either induction at 39 weeks or to “expectant management,” which meant until labor began spontaneously, was induced, or the trial participant underwent planned cesarean.³²  They found that routine induction decreased cesarean rates from 22% to 19%, or 3 fewer cesareans per 100 women, and resulted in similar rates of newborns experiencing one or more adverse outcomes (5% vs. 4%) and similar rates of  newborn admission to an intensive care nursery (12% vs. 13%).

The trial has some weaknesses, and if you’re interested in finding out more about them, I’ve discussed them under “Taking a Deeper Dive” below, but the main problem is that the trial compared a frying pan to a fire. It wasn’t that 39-week induction got such good results; it was that the medical management approach got poor results in both groups but worse results with expectant management.

We know this because we have an alternative model of care we can use for a comparison. Unlike medical management, physiologic care works from the principle that the best outcomes will be achieved by care that supports the unfolding of the natural process and reserves medical intervention for situations where this proves inadequate. Studies of birth center and home births, where women are attended by midwives who practice in this alternative model, report cesarean rates ranging from 8 to 13% in 1^st-time mothers at similarly low risk to those in the trial, or 6 to 11 fewer cesareans per 100 than the 19% rate the trial reported with induction at 39 weeks.^{3, 6, 9, 37, 39-41, 61}

Newborn outcomes with medical management were inferior as well. Despite being healthy women carrying healthy babies, 12% of induction-group babies were admitted to intensive care versus 3% of babies in an analysis of U.S. home and birth center births.¹⁸ This is not quite an apples-to-apples comparison because the home and birth center study also included mothers who had had babies before, and 1^st-time mothers are more likely to end up with babies in special care nurseries. Still, I doubt that 1^st-time mothers would have quadruple the odds.

In other words, we have obstetricians claiming that inducing ultra-low-risk 1^st-time mothers at 39 weeks is best practice despite 1 in 5 women ending up with a cesarean, and more than 1 in 10 of their babies ending up in intensive care. I say that all it shows is that the 39-week induction “frying pan” comes out slightly ahead of the expectant management “fire.”

The Take-Away

In ordinary times, I would argue that the savvy woman’s best option is to get out of the kitchen and find care providers who only induce labor for medical indications—these, by the way, are more likely to be midwives—but these aren’t ordinary times. It remains true that you are better off with a care provider who only intervenes medically when supportive care or just having patience hasn’t resolved the problem, but nowadays induction permits you and your birth partner to be tested for the COVID-19 virus and cleared before admission. Otherwise, you and your partner will be tested when you arrive in labor and will likely be considered “persons under investigation” until tests come back, which takes time. During the interim, you will be treated as if you and your partner are infected, which can be problematic. With that in mind, here are my suggestions:

If you want to start labor naturally, ask your care provider if you and your partner can come in for testing once you think you have begun labor, and you can have a vaginal exam, the plan being to return home if you aren’t far enough along in labor to be admitted, which, if this is a first baby, will likely be the case. That way, your test results may be in by the time you have made enough progress to be admitted, or they will come in shortly thereafter. You may end up making more than one trip to the hospital or your care provider’s office to be checked before you are ready to be admitted; however, the inconvenience may be worth it if it avoids an induction you don’t need.

If induction seems like the right decision, the issue becomes maximizing the probability of having an uneventful labor that ends in spontaneous vaginal birth. Here are some ways to do that:

• Decline induction if your body isn’t ready for labor (Bishop score < 8). If your body is ready to go, your odds of cesarean are the same as with spontaneous labor onset. Also, you won’t need a cervical ripening agent and therefore won’t run the risk of experiencing its adverse effects.
• Decline having your bag of waters broken as part of the induction. If membranes are intact and the induction isn’t working, you can stop, go home, and try another day. Once membranes are ruptured, you are committed to delivery one way or the other.
• Request that oxytocin be administered according to the regimen recommended on the package. “Start low and go slow” eliminates much of the risk of experiencing oxytocin’s complications.
• Request that the oxytocin drip be turned off once you are in actively progressing labor. In many cases, when the drip is turned off, your body will take over and labor will continue under its own steam. If it doesn’t, the drip can always be turned on again.⁵⁶ Discontinuing oxytocin decreases likelihood of abnormal contractions and abnormal fetal heart rate and increases likelihood of vaginal birth.^{7, 56}
• Request that your care provider follow the induction and labor management practices jointly recommended by the American College of Obstetrics & Gynecology (ACOG) and the Society for Maternal-Fetal Medicine (SMFM).² These are:
  • Provided mother and baby are tolerating labor, IV oxytocin should be administered for at least 12-18 hours before diagnosing induction failure.
  • Active labor should be defined as achieving 6 cm dilation.
  • Slow, but progressive, labor is not an indication for cesarean. A diagnosis of arrested labor should be reserved for failure to progress in the active phase for at least 4 hours with adequate uterine activity and 6 hours with inadequate activity and IV oxytocin administration.
  • Provided mother and baby are tolerating labor, 1^st-time mothers should be allowed to push for at least 3 hours and longer if they have an epidural or with a poorly positioned baby so long as progress is being documented.

Taking a Deeper Dive

What effect does inducing labor have on the cesarean rate?

While obstetricians recognized that induction increased likelihood of cesarean, they attributed the cause to the reasons for inducing, not to the procedure itself. However, studies of elective induction, meaning induction without medical indication, consistently find that compared with women beginning labor on their own, induction increases cesareans even after adjustment for factors such as birthweight and gestational age. First-time mothers roughly double their odds of cesarean with excesses ranging from 3 to 31 more women per 100.^{5, 8, 12, 21, 22, 24, 28, 38, 44, 46, 47, 50, 57, 60, 62, 63, 65, 66} Elective induction also increases cesareans in women who have had vaginal births before, but to a much smaller degree.^{5, 34, 35, 38, 42, 62} The effect on cesarean rate isn’t mitigated by cervical ripening agents,^{23, 26, 27, 43, 44, 49, 52, 55, 60} which isn’t surprising because softening the cervix isn’t the only factor involved in preparing for labor.

In response to these studies, obstetricians argued that the question isn’t whether women do better with induced or spontaneous labors but whether women reaching term are better off with induction compared with continuing the pregnancy to some later date.¹⁵ Most, though not all, studies comparing induction in any given week versus pregnancies continuing beyond that week—which could mean either labor starting on its own or induction or scheduled cesarean after that week—report somewhat fewer cesareans with induction.^{16, 20, 45, 54} However, critics have pointed out that comparing induction in a particular week with ongoing pregnancy after that week leaves out women who began labor on their own during that week. If you include those women, women are more likely to have cesareans with induction than with waiting for labor.^{4, 20, 27, 30}

Another problem with the “induction versus continuing pregnancy” studies is that many women in the ongoing pregnancy group will end up being induced. As we saw above, the more women who are induced in the expectant management group, the worse expectant management looks because induction increases likelihood of cesarean. Proponents of routine induction assume that these inductions are inevitable, but are they?

Does the cesarean rate rise inevitably with advancing pregnancy for reasons inherent in pregnancy?

The main rationale for inducing everyone at 39 weeks is the belief that the cesarean rate increases with advancing pregnancy for reasons intrinsic to pregnancy. The baby will grow too big to birth or the deteriorating placenta will render the baby unable to tolerate the stress of labor. Expectant management will only end in substantial numbers of women being induced later who will have even higher cesarean rates as a result, and cesarean rates will rise with gestational age even with spontaneous onset. It is true that many women will end up being induced. A multi-year analysis of just under 230,000 deliveries at 19 U.S. hospitals found that only a little over half of women begin labor on their own.⁶⁷ It is also true that the cesarean rate soars in 1^st-time mothers with advancing gestation, but the culprit is medical management, not an inherently faulty process. How do we know this?

• Studies of 1^st-time mothers report wide variation in cesarean rates that can’t be explained by differences in the characteristics of the women. For example, as you can see in the table, Cheng (2012) and Rasmussen (2011) were both studies of low-risk women, but cesarean rates differed greatly while Darney (2013), a study that included women with medical complications, reported cesarean rates similar to those in Cheng (2012), a study of low-risk women only.^{16, 20, 54}

Along similar lines, a study reported similar cesarean rates in 1^st-time mothers induced for medical reasons and in women induced electively,⁵ and another found substantially lower cesarean rates in women induced for medical reasons than women induced electively.³¹ You would expect that women being induced for medical problems would have higher cesarean rates than healthy women undergoing induction for non-medical reasons. If you see variations in cesarean rates that can’t be explained by the characteristics of the women, then management style is responsible, not factors intrinsic to study participants or advancing gestation at term.

• The largest trial that looked at routinely inducing women at 41 weeks reported that 26% of 1^st-time mothers beginning labor on their own had cesareans as did 5% of women who had only had vaginal births before.³³ These were all healthy women carrying one, head-down, healthy baby who were admitted in labor. In other words, they had not one reason at hospital admission that would predict possible need for cesarean. If you find extraordinarily high cesarean rates in ultra-low-risk women, then something is wrong with labor management, not the women.
• Two large U.S. studies reported that the cesarean rate was stable in healthy 1^st-time mothers in weeks 37 through 40 but then leapt upward in the 41^st week, and one of them found it leapt upward again from week 41 to week 42.^{14, 17} Women and babies who are healthy at 39 weeks aren’t very likely to develop a complication in the ensuing weeks, and few babies will outgrow their mother’s ability to birth them.^{4, 19, 45} If you see a large increase in cesarean rate over a few days in healthy women, then what changed was care provider perception and management, not health status or the size of the baby.

Does routine induction improve newborn outcomes?

As with reducing cesareans, the idea that babies would do better with induced labors is counterintuitive. For one thing, induced labors can cause contractions that are overly long, strong, and close together compared with natural contractions.^{1, 11, 25, 36, 59} Induced contractions should be more, not less, difficult for the baby to tolerate. For another, the baby’s readiness for birth largely dictates when labor begins. Induction overrides that process, which means some babies will be born not quite ready for the outside world. Still, a few studies have reported small improvements overall in respiratory complications or special-care nursery admissions or in improvements in some weeks but not in others.^{4, 32, 53} That being said, if the theory that routine induction improves newborn outcomes is correct, then a high induction rate should correlate with better newborn outcomes, but a multi-hospital analysis found no correlation.²⁹

We must also consider that high induction rates in the groups undergoing expectant management in the studies of routine induction versus expectant management and the consequent high cesarean rates are a confounding factor. The higher the cesarean rate in the planned expectant management group, the worse expectant management looks because poor condition at birth is more likely.

What are the weaknesses of the trial that claims to settle the debate?

The crucial question for the trial allocating women to routine induction at 39 weeks versus expectant management is: “What percentage of women were induced in the planned expectant management group?” because as we have seen, the higher the percentage, the worse expectant management will look. The study’s report doesn’t tell us, but from what it does tell us, it looks to be a substantial number.³² It tells us the median pregnancy duration, meaning half delivered before and half after, with planned expectant management was 40 weeks 0 days, but the median pregnancy duration in 1^st-time mothers reaching term with an uncomplicated pregnancy is 41 weeks 1 day, or 8 days longer.⁵¹ It also tells us that three-quarters of the expectant-management group had their babies by 41 weeks 0 days, but the “41 week 1 day median” in healthy women tells us that you would expect only half of this population to have had their babies by 1 day later. The other tip-off is that while having an unripe cervix at 39 weeks increased the odds of cesarean, the 39-week induction-group women had lower cesarean rates than women in the planned expectant management group. Surely, the cervix would have ripened before labor began had women in the expectant management group been allowed to start labor on their own, which should have given them the advantage. The only logical explanation is that a substantial percentage of expectantly managed women underwent mostly unnecessary inductions with an unfavorable cervix.

In addition, according to a commentary on the trial,⁴⁸ labor was to be managed according to ACOG & SMFM’s joint recommendations (see the “Take Away” bullets above for detail), but typical labor management differs from these guidelines in ways that would decrease likelihood of vaginal birth. That means that you won’t see the same results with typical obstetric management as were seen in the trial.

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