If the baby isn’t preterm (less than 37 weeks), many practitioners induce labor when the amniotic sac surrounding the baby breaks and contractions don’t quickly follow. The reason for this is to prevent infection in mothers and especially babies once the barrier that prevents microbes from entering the uterus is gone. But inducing labor, as with any intervention into the physiologic process, isn’t harmless, which raises the question of whether induction is justified. In this post, we’ll look at:
- How likely and how serious is maternal and newborn infection?
- Is infection preventable without resorting to induction?
- Does testing positive for Group B strep change the picture?
Then, as usual, I’ll end with “Your Takeaway”: practical strategies for applying what you have learned.
How Likely Is Infection?
My source for answering “How likely is infection?” is a systematic review, a “study of studies” that pools data from multiple studies on a particular topic. The reviewers pooled results from randomized controlled trials in which participants (6,864 in all) whose membranes had released at 37 weeks or later were assigned by chance to either immediate induction or to waiting for labor.8 The review found that, yes, waiting for labor increased the probability of newborn and maternal infection. However, as with so many studies founded in the medical approach to labor management, the devil is in the details.
Starting with maternal infection, 6 percent of participants assigned to immediate induction experienced symptoms of uterine infection compared with 11 percent of those assigned to await labor, or 5 fewer participants per 100 assigned to immediate induction. But while that’s of some concern, it’s not a major one because uterine infections are readily treated with antibiotics.
What’s more, there’s a question of how many of the participants were experiencing true infections. The reviewers compared incidence of maternal “infectious morbidity” between the two groups, which could be either chorioamnionitis, defined as “inflammation of the membranes,” or endometritis, defined as “generally a postpartum infection.” In all but one trial, which contributed a mere 566 participants, chorioamnionitis could be diagnosed by the occurrence of fever alone. The problem with allowing fever as the sole symptom is that fever can be caused by factors other than infection. In particular, epidurals cause non-infectious fevers.6 I can’t help but think that the reviewers used “infectious morbidity” and “inflammation of the membranes,” rather than outright “infection,” because they knew that fever was a tenuous indicator of infection in the absence of other symptoms.
The review doesn’t distinguish between maternal infection diagnoses based on fever alone and those with other indicators, but the largest trial in the review—5,041 participants, or 73 percent of all participants—did.4 That trial found that the overall infection rate was 5 percent with induction compared with 8 percent with awaiting labor, but when incidence was confined to participants who either had a high white-blood-cell count or foul-smelling amniotic fluid, they fell to 1 percent with induction versus 2 percent with awaiting labor. Using fever, then, in the absence of other diagnostic criteria, gives the misimpression that awaiting labor is more of a maternal risk than it really is.
Newborn infection rates, by contrast, are of major concern. Newborn infections can be severe because of their immature immune systems. Among newborns, the review reported that definite or probable newborn infection (as defined by positive cultures or symptoms) occurred in 3 percent of newborns in the immediate induction group versus 4 percent in the await labor group.8 While the difference was statistically significant, meaning that statistical calculation showed it probably wasn’t due to chance, the absolute difference is quite small, only 1 fewer infection per 100 in the immediate induction group.
This, however, brings us to a bigger issue affecting both maternal and newborn infection rates in the review: the increase in infections with awaiting labor is only seen in participants who had vaginal exams. In other words, the increase with awaiting labor is iatrogenic, meaning caused by doctors.
As you can see from the bar graphs, once vaginal exams are factored in, the difference in newborn infection rates disappears, and the difference in maternal infectious symptoms is no longer statistically significant, meaning it could have been due to chance—and that’s without considering that in many cases, the sole symptom of maternal infection would have been fever, which might not have been an infection at all.
Is Infection Preventable without Resorting to Induction?
That last finding answers the question of whether infection is preventable without resorting to induction. It is. Keep fingers out of the vagina, and time isn’t an issue.
You might be wondering why vaginal exams make a difference since the examiner wears sterile gloves. Here’s why: the examiner’s glove may be sterile, but the probing finger carries vaginal microbes up and deposits them at the cervical inlet. Absent intact membranes, the microbes can enter the uterus and start an infection. Compared with women who were induced, women assigned to await labor experienced longer times between release of membranes and birth and therefore had more vaginal exams to evaluate progress. That increased the opportunity for an infection to begin and set in.
You might also be wondering if labor progress can be monitored without them. It can. A speculum exam can let care providers know what’s going on with the cervix if need be. And while it’s usual with the medical approach to perform vaginal exams at regular intervals once labor gets going, it isn’t necessary. Vaginal exams can be reserved for those times when the assessment is needed for a decision about care, in which case they pose little risk because infection correlates with their number.10
Does Testing Positive for Group B Strep Change the Picture?
This brings us to the final question: Does testing positive for Group B Strep change the picture? Group B streptococcus is a bacterium that lives mostly harmlessly—it can sometimes cause urinary infections—in the rectum and vagina in 10-30 percent of pregnant women and birthing people. It can, however, infect the unborn baby, causing severe illness in some cases in the days after birth.2 For this reason, the American College of Obstetricians and Gynecologists’ (ACOG’s) guidelines on Group B strep recommend that all women and pregnant people be tested at 36 to 37 weeks gestation and that those testing positive be given IV antibiotic in labor as a preventive measure.2 This policy has greatly reduced the incidence of newborn Group B strep severe illness. (For more information on identification and treatment of Group B strep carriers, which is a less clear cut issue than I can go into here, I recommend Group B Strep Explained by Sara Wickham.) The guidelines also recommend inducing labor immediately if the membranes release, which raises the question of whether testing positive for Group B strep should be an exception to the finding that induction doesn’t reduce infection provided vaginal exams are avoided. I contend that it isn’t. Here’s why:
ACOG’s guidelines cite two studies as their source for that recommendation. One is a study of preterm membrane release, but preterm babies are much more vulnerable to infection and to experiencing severe consequences of infection, so outcomes in this study can’t be applied to term infants. The other study was published in 1997.5 It assigned women at term whose amniotic sac had released to either immediate induction or to await labor, and it found that women who tested positive for Group B strep were more likely to have infants who developed infections. Problem #1 is that this study was conducted at a time when few pregnant women were tested for Group B strep. Some may have been known carriers before hospital admission, but mostly investigators only knew Group B strep status after the birth because it was determined by testing study participants at hospital admission, and results weren’t known until days later. Problem #2 is that giving IV antibiotics in labor wasn’t common. Only one-quarter of the women who turned out to be Group B strep carriers received IV antibiotics. Finally, problem #3 is that they had multiple vaginal exams. In other words, the results of this trial do not apply to today’s practices.
This brings us to the practical section of this post: formulating a plan based on your preferences and circumstances. I’ve grouped my suggestions according to your main decision-making branches, these being: you prefer to await labor; you prefer induction or have a medical indication for induction apart from simply having had the sac break; or you test positive for Group B strep.
Hopefully, you aren’t reading this because membranes have released. If you are, the recommendations in the first two bullets don’t apply. That being said, the rest of my suggestions should still prove helpful.
You prefer to await labor:
- If they don’t already, choose or change to care providers who either don’t routinely induce labor immediately if the amniotic sac releases at term or who respect your right to make informed decisions about your care. It is, as they say, better to switch than fight.
- Hire a doula. If switching to care providers more aligned with your preference—or who are willing to work with you if they aren’t—isn’t feasible, having a doula is especially important. Doulas are a valuable addition to your team for any labor, but having someone in your corner to help you with your decision-making process is crucial if you may be fighting an uphill battle.
- If you’re looking for a middle position between waiting for labor indefinitely and inducing ASAP, delay induction for 24 hours. You have a 95 percent probability of labor starting within 24 hours,8 and ACOG’s guidelines state:1
The choice of expectant management for a short period of time may be appropriately offered. … A period of 12-24 hours of expectant management is reasonable as long as the clinical and fetal conditions are reassuring.
- Decline vaginal exams until established in active labor. ACOG’s prelabor rupture of membranes guidelines back you on this too:1
Digital [with the fingers] examination should be used sparingly and judiciously.
- Decline internal fetal monitoring (the baby’s heart rate is picked up through an electrode that catches under the skin of the baby’s scalp). The exception would be concern about the baby and external monitoring isn’t providing adequate information.
- Decide if you’re going to wait for labor at the hospital or at home. Waiting for labor at home is more comfortable and less stressful but requires that you take more responsibility. You will want to discuss what to watch for with your care providers as well as precautions to take to avoid infection, when to come to the hospital if labor begins, and how long to wait if it doesn’t.
- Decline routine antibiotics. ACOG’s guidelines recommend against routine administration of antibiotics except when testing positive for Group B strep.1 Antibiotics aren’t harmless. By indiscriminately killing off all bacteria, they interfere with colonization by harmless and helpful bacteria, aka, establishing a healthy microbiome, in the infant. Antibiotic treatment also increases the risk of thrush, an opportunistic yeast infection, occurring in mother, baby, or both.9 Thrush can make the nipples and the baby’s mouth extremely sore, which can play merry hell with breastfeeding.
You prefer induction or have a medical indication for induction:
- Decline cervical ripening agents. These are agents that convert a cervix that is unfavorable for labor, i.e., long, thick, and firm, to one more favorable, but their use hasn’t been shown to affect the cesarean rate compared with induction with IV oxytocin alone (aka Pitocin or Syntocinon). Moreover, some strategies (vaginal treatment with prostaglandin E2, inserting a balloon catheter into the cervix) are associated with increased probability of infection.1, 4, 7
- Decline a cesarean for progress delay until you have had 12 to 18 hours of adequate contractions. Also recommended in ACOG’s guidelines,1 this ensures enough time to determine if the induction is going to work. Even then, the decision should be made on an individual basis: Is progress being made, even if slow? Are mother and baby tolerating labor? What’s been tried to promote progress, e.g., walking, position changes, working through fears?
You test positive for Group B strep:
- Consider whether you will agree to immediate induction or if you want to delay for some prearranged period to see if labor starts on its own. As we saw above, your baby isn’t at increased risk of Group B strep infection provided fingers are kept out of the vagina, and induced labors can be harder on you and the baby.
- If you decide to agree to induction, consider whether you want to hold off until after receiving the full 4-hour dose of IV antibiotic. ACOG’s Group B strep management guidelines recommend not delaying induction solely to provide the full 4-hour course of IV antibiotics despite acknowledging that a shorter duration is less effective.2 But sometimes a labor will take off once an induction is started. Against that possibility, why not wait to complete the antibiotic course before starting the induction?
- Decline vaginal exams before labor begins; limit them once you are in labor. As I said earlier, a speculum exam can let care providers know what’s happening with the cervix, and while usual hospital management is to perform vaginal exams regularly in labor, infection correlates with their number.10 Request that vaginal exams be limited to those times when information is needed for a decision about your care.
- Decline internal monitoring. The exception would be concern about the baby and external monitoring isn’t providing adequate information.
- If you are planning a home or birth center birth, find out if you can get your IV antibiotic treatment at home or the birth center. Certified nurse- and direct-entry midwives, that is, those with the letters C.P.M. (Certified Professional Midwife), C.N.M. (Certified Nurse-Midwife), or C.M. (Certified Midwife) after their names, have learned how to manage IVs as part of their training,3 personal communication), and many will provide this treatment. It may also be possible to get your antibiotic treatment on an outpatient basis at your backup hospital.
- ACOG. Prelabor Rupture of Membranes: ACOG Practice Bulletin, Number 217. Obstet Gynecol 2020;135(3):e80-e97.
- ACOG. Prevention of Group B Streptococcal Early-Onset Disease in Newborns: ACOG Committee Opinion, Number 797. Obstet Gynecol 2020;135(2):e51-e72.
- Ehrlich K. Re: Question about CPM training. In: Goer H, ed.; May 29, 2023.
- Hannah ME, Ohlsson A, Farine D, et al. Induction of labor compared with expectant management for prelabor rupture of the membranes at term. TERMPROM Study Group. N Engl J Med 1996;334(16):1005-10.
- Hannah ME, Ohlsson A, Wang EE, et al. Maternal colonization with group B Streptococcus and prelabor rupture of membranes at term: the role of induction of labor. TermPROM Study Group. Am J Obstet Gynecol 1997;177(4):780-5.
- Jansen S, Lopriore E, Naaktgeboren C, et al. Epidural-Related Fever and Maternal and Neonatal Morbidity: A Systematic Review and Meta-Analysis. Neonatology 2020;117(3):259-70.
- Lin MG, Nuthalapaty FS, Carver AR, et al. Misoprostol for labor induction in women with term premature rupture of membranes: a meta-analysis. Obstet Gynecol 2005;106(3):593-601.
- Middleton P, Shepherd E, Flenady V, et al. Planned early birth versus expectant management (waiting) for prelabour rupture of membranes at term (37 weeks or more). Cochrane Database Syst Rev 2017;1:CD005302.
- Ohlsson A, Shah VS. Intrapartum antibiotics for known maternal Group B streptococcal colonization. Cochrane Database Syst Rev 2009(3):CD007467.
- Seaward PG, Hannah ME, Myhr TL, et al. International Multicentre Term Prelabor Rupture of Membranes Study: evaluation of predictors of clinical chorioamnionitis and postpartum fever in patients with prelabor rupture of membranes at term. Am J Obstet Gynecol 1997;177(5):1024-9.