Research and Evidence
NOTE: For guiding decisions about care, Childbirth Connection gives priority to systematic reviews. These rigorous summaries of best available studies are the most trustworthy way to know the benefits and harms of specific practices.
This page provides you with the best available evidence about inducing labor before it starts on its own. We strongly encourage you to read the Maternity Care section for more information about maternity care decision-making and the importance of high-quality care.
What does the research say about labor induction?
The safety and effectiveness of labor induction depend on a lot of factors, including your health, your baby’s health, if you’ve given birth before, the timing of the induction, the method used for inducing labor, the birth setting and its care patterns, and more. Therefore, it’s hard for anyone to predict exactly what the risk and benefits will be for any individual woman and her baby.
That being said, research conducted by King and colleagues in 2010King, V., Pilliod, R., & Little, A. (2010). Rapid review: Elective induction of labor. Portland: Center for Evidence-based Policy. found that:
- Elective induction (induction without a well-supported medical reason) before 39 weeks clearly increases risks for babies. These risks include breathing problems, infection and admission to a neonatal intensive care unit (NICU). Much brain growth and development happens in the last weeks of pregnancy, and babies born even a few weeks before their due dates have more learning and behavioral problems than babies born after 39 weeks.
- Elective induction before 41 weeks increases the chance of having a C-section if the cervix has not already softened and started to open on its own, especially in first-time mothers. And using medications or procedures to soften the cervix does not decrease the chance of a C-section.
- Women in induced labor are more likely to ask for an epidural for pain relief than women who go into labor on their own. Epidurals have their own risks and change the experience of labor: Many other interventions are used to monitor, prevent or treat their side effects.
Induction methods also change the type of care and monitoring a woman will need in labor. Induction involves having at least one intravenous (IV) line, continuous electronic fetal monitoring and medications after birth to reduce the risk of hemorrhage (too much bleeding). The IV and fetal monitoring equipment make it harder to move around in labor, which can increase pain. Many hospitals don't allow women to eat or drink during induction of labor.
Does induction ever improve health outcomes for the mother, baby or both?
A 2009 systematic review of the research on inductionMozurkewich, E., Chilimigras, J., Koepke, E., Keeton, K., & King, V.J. (2009). Indications for induction of labour: A best-evidence review. BJOG, 116(5), 626-636. found only two conditions for which induction seems to improve health outcomes. A later study answered an open question in this systematic review and identified a third situation in which induction can improve health outcomes.Koopmans, C.M., Bijlenga, D., Groen, H., et al. (2009). Induction of labour versus expectant monitoring for gestational hypertension or mild pre-eclampsia after 36 weeks' gestation (HYPITAT): A multicentre, open-label randomised controlled trial. Lancet, 374(9694), 979-988.In all three cases, differences in health outcomes were small and the studies left some important questions unanswered. Here are the three situations:
- Pregnancy lasting beyond 41 weeks: Various studies have compared induction of labor at or after 41 weeks with "watchful waiting" that involves repeated tests of fetal wellbeing between 41 and 42 weeks. Taken together, the studies suggest that for every 369 women who had labor induced between 41 and 42 weeks, one stillbirth or neonatal death may be prevented. The risk of meconium aspiration syndrome (an illness that causes serious breathing problems in the baby) may also be slightly lower. Induction between 41 and 42 weeks does not seem to increase the risk of C-section, and some studies have shown that it reduces this risk.
- Pre-labor rupture of membranes (PROM) at term (37-42 weeks): This is when membranes break on their own from 37 weeks onward, and labor hasn’t begun. A large randomized controlled trial compared immediately trying to induce labor with waiting up to three days for labor to begin and only inducing sooner if a complication developed. The study found that inducing right away was associated with a lower chance that the mother would develop an infection or the baby would go to the NICU. Immediate induction did not affect the likelihood of C-section, newborn infection or other important outcomes. However, most women in the watchful waiting group had vaginal exams before labor began, and those who carried Group B Strep (a bacterium that may be present in a woman's vagina and raises the risk of infection for the baby) were not given antibiotics to prevent infection. Many caregivers and researchers believe that avoiding vaginal exams until labor started and providing antibiotics to women with Group B Strep might have prevented the infections reported in the trial. These are standard practice in U.S. maternity care settings today.
- Increased blood pressure near the end of pregnancy: High blood pressure that develops in pregnancy may occur without other symptoms or signs (gestational hypertension) or with protein in the urine (preeclampsia, a more dangerous condition). High blood pressure can affect the flow of oxygen to the baby, increase the chance of complications during labor and lead to rare but very serious outcomes like stroke and seizures.
Researchers studied outcomes of women at or beyond 36 weeks of pregnancy who had gestational hypertension (diastolic blood pressure, the second number in a blood pressure reading, between 95 and 110) or mild preeclampsia (diastolic blood pressure between 90 and 110 and protein in the urine). The study found that inducing labor right away improved maternal outcomes. However, they defined "poor maternal outcome" to include any cases where women developed severe high blood pressure. Very few of these women experienced serious health problems as a result of the blood pressure increase. There were no significant differences in the number of serious problems like seizure, need for intensive care or postpartum hemorrhage, although the study was too small to show whether there were differences in these uncommon outcomes. There were also no significant differences in newborn outcomes, although a later study showed that neonatal intensive care admission, need for artificial ventilation (a machine to help the baby breathe), low birth-weight, and jaundice were more common the earlier a woman with mild gestational hypertension was induced, with best outcomes in the group induced after 38 weeks.Koopmans, C.M., Bijlenga, D., Groen, H., et al. (2009). Induction of labour versus expectant monitoring for gestational hypertension or mild pre-eclampsia after 36 weeks' gestation (HYPITAT): A multicentre, open-label randomised controlled trial. Lancet, 374(9694), 979-988; Barton, J.R., Barton, L.A., Istwan, N.B., et al. (2011). Elective delivery at 34(0/7) to 36(6/7) weeks' gestation and its impact on neonatal outcomes in women with stable mild gestational hypertension. American Journal of Obstetrics & Gynecology, 204(1), 44.e1-44.e5.
In the randomized controlled trial, women with mild preeclampsia (versus the more mild gestational hypertension), women having their first baby, and those with the least amount of cervical dilation were the most likely to benefit from early induction. This is most likely because preeclampsia is a more serious condition than gestational hypertension and first-time mothers and those who haven't begun dilating would have remained pregnant longer, providing more opportunity for their condition to worsen.
Is labor induction a possible tool for cesarean reduction?
Labor induction has been associated with increased likelihood of cesarean birth for some groups of women: first-time mothers and women whose cervix is not soft and ready to open (“ripe”).Caughey, A.B., Sundaram, V., Kaimal, A.J., Cheng, Y., Gienger, A., Little, S., Lee, J., Wong, L., Shaffer, B., Tran, S., Padula, A., McDonald, K., Long, E., Owens, D., & Bravata, D. (2009). Maternal and Neonatal Outcomes of Elective Induction of Labor. Evidence Report/Technology Assessment No. 176. (Prepared by the Stanford University-UCSF Evidenced-based Practice Center under contract No. 290-02-0017.) AHRQ Publication No. 09-E005. Rockville, MD.: Agency for Healthcare Research and Quality; Grobman, W. (2007). Elective Induction: When? Ever? Clinical Obstetrics & Gynecology, 50(2), 537-546. For other women or for women overall at full term, systematic reviews have found that labor induction either does not impact the likelihood of cesarean birthSaccone, G., & Berghella, V. (2015). Induction of labor at full term in uncomplicated singleton gestations: A systematic review and metaanalysis of randomized controlled trials. American Journal of Obstetrics & Gynecology, 15, 00356-7. or is associated with reduced likelihood of cesarean birth.Mishanina, E., Rogozinska, E., Thatthi, T., Uddin-Khan, R., Khan, K., & Meads, C. (2014). Use of labour induction and risk of cesarean delivery: A systematic review and meta-analysis. Canadian Medical Association Journal, 186, 665-673; Nicholson, J., Kellar, L., Henning, G., Waheed, A., Colon-Gonzalez, M., & Ural, S. (2015). The association between the regular use of preventive labour induction and improved term birth outcomes: Findings of a systematic review and meta-analysis. BJOG: International Journal of Obstetrics and Gynecology, 12, 773-784. Quality improvement programs to avoid elective induction in first-time mothers with an “unripe” cervix (not soft and ready to open) have successfully reduced cesarean rates.King, V., Pilliod, R., & Little, A. (2010). Rapid review: Elective induction of labor. Portland: Center for Evidence-based Policy. This diversity of conclusions is confusing to pregnant women and others!
Some are beginning to talk about inducing labor when there is no medical reason as a method of cesarean reduction. Childbirth Connection does not support induction without a clear medical reason, including for cesarean prevention, because:
- Researchers need to make sense of the different conclusions about cesarean after induction and factors that could influence results (e.g., how studies were conducted, which women were included, and what other practices were used in the research settings).
- Labor induction is a major intervention that cuts short important preparations for safe, smooth labor and beyond that take place in the body of a woman and her fetus up to the time when labor starts on its own.
- Labor induction exposes both woman and fetus to the drugs and other practices used to start labor.
- We do not at present understand well the possible harms of making pregnancy shorter and using the various methods for starting labor. These may have an adverse effect on important outcomes such as severe bleeding after birth (postpartum hemorrhage), getting breastfeeding started, maternal mood, maternal behavior and mother-baby attachment. You can stay on the safe side by avoiding these when there is no clear need.
- As shown in our cesarean birth section, there are many clearer and safer ways to reduce the likelihood of cesarean birth.
What common reasons given for inducing labor are not supported by research?
For a surprising number of conditions, the effectiveness of induction has not been proven.Mozurkewich, E., Chilimigras, J., Koepke, E., Keeton, K., & King, V.J. (2009). Indications for induction of labour: A best-evidence review. BJOG, 116(5), 626-636. Yet many women with these conditions have induced labor because they believe it will be good for them or their babies. More research is needed to confirm the benefits and harms of induction in these situations:
- Preterm prelabor rupture of the membranes (PPROM): In this situation, the membranes break on their own before pregnancy week 37, and labor has not begun. Eight studies with a combined total of 1,230 babies of women with ruptured membranes between 34 and 37 weeks of pregnancy found no advantages for induction compared with waiting for labor with respect to C-section or infection or breathing problems in babies.
- Twin pregnancy: A single, small randomized controlled trial compared routine induction at 37 weeks with waiting for labor and found no differences in important health outcomes. More research is needed.
- Gestational diabetes requiring insulin: One trial looked at the outcomes of 200 women randomized to either be induced at 38 weeks or wait for labor. Those who waited were more likely to have large babies. There were no differences in health outcomes for the mothers or babies. The trial may have been too small to detect these differences.
- Intrauterine growth restriction (IUGR) at term: In this situation, the baby appears to be smaller than we would expect at or beyond 37 weeks of pregnancy. Two trials involving a combined 683 women found no benefit or harm to induction for suspected IUGR at term. More and larger trials are needed.
- Oligohydramnios (too little amniotic fluid): A single, small randomized controlled trial compared induction of labor with watching fetal well-being closely until 42 weeks for women with suspected low amniotic fluid at 41 weeks. The women were healthy and did not have other risk factors or complications. The study found no difference in maternal or newborn outcomes, but was too small to detect some important differences that may exist. No trials of induction for low fluid levels in women with otherwise healthy pregnancies at other gestational ages were found.
For other conditions, the available evidence suggests induction is ineffective, harmful or both.Mozurkewich, E., Chilimigras, J., Koepke, E., Keeton, K., & King, V.J. (2009). Indications for induction of labour: A best-evidence review. BJOG, 116(5), 626-636. Despite the research, many providers continue to recommend induction because:
- They believe the baby will get too big (suspected macrosomia). According to a systematic review of several studies involving more than 3,700 women, inducing labor when the provider suspects that the baby is large does not improve neonatal (baby’s) outcomes and appears to increase the chance that the woman will have a C-section.
- There is intrauterine growth restriction before 37 weeks. In this situation, the baby appears to be smaller than we would expect before pregnancy week 37. A large, multi-center randomized controlled trial of more than 1,000 women with growth-restricted fetuses between 24 and 36 weeks and abnormal Doppler artery blood flow showed that induction increased the likelihood of C-section. In addition, babies born before 31 weeks in the induction group were more likely to have severe disabilities at age 2 than babies born before 31 weeks in the group that waited for labor.
Which induction method is the safest and most effective?
It is very difficult to know the safest and most effective way to induce labor in a particular woman. The research provides only a few clear answers because most studies do not compare the different methods to one another. Also, not enough research shows the effects of different combinations of methods used in the same woman.
The best induction method depends on whether you have begun dilating, whether your water has broken, whether you or your baby have health problems and other factors. Different methods have different risks and benefits. Some risks and benefits are unknown because there is not enough research.
There are many ways women or care providers may try to induce labor before going to the hospital. Most of these have not been studied closely. Here are some details on the different methods used to start labor and how effective they are based on a systematic review by Mozurkewich et al., 2011.Mozurkewich, E., Chilimigras, J.L., Berman, D.R., Perni, U.C., Romero, V.C., King, V.J., & Keeton, K.L. (2011). Methods of induction of labour: a systematic review. BMC Pregnancy and Childbirth, 11(84), 1-19.
- Hypnosis: not effective, compared with doing nothing
- Homeopathy: not effective, compared with doing nothing
- Sexual intercourse: not effective, compared with doing nothing
- Sweeping/stripping membranes (office procedure done with a vaginal exam): not effective, compared with doing nothing
- Acupuncture: not effective, compared with doing nothing
- Breast stimulation: increases the likelihood of starting labor, but more research is needed to understand safety (there are concerns that strong contractions could reduce oxygen flow to the fetus, although the study that raised this concern was done in women with high-risk pregnancies)
- Castor oil: effective at starting labor, but does not decrease the chance of having a C-section. Castor oil causes nausea and diarrhea in most women. More research is needed to understand safety.
Women who are planning a hospital induction of labor need to decide which methods to use. An important factor in making the decision is the woman's "Bishop score." This score measures the qualities of the cervix and the position of the baby to estimate how ready the woman and baby are for labor.
If the Bishop score is 6 or higher, the induction is likely to begin with synthetic oxytocin (“Pitocin”), breaking the bag of water or both. There are important differences between the effects of the woman’s own oxytocin and the effects of synthetic oxytocin. Unfortunately, there is not enough research to understand possible effects of synthetic oxytocin on such outcomes as excess bleeding after birth, breastfeeding, and maternal mood after birth.
- We do not now have trustworthy evidenceGrivell, R.M., Alfirevic, Z., Gyte, G.M.L., & Devane, D. (2015). Antenatal cardiotocography for fetal assessment. Cochrane Database of Systematic Reviews, 9. about whether breaking the bag of water alone is effective in starting labor, Breaking the bag of water is a commitment to getting the baby born because this increases the risk of infection.
- Synthetic oxytocin (“Pitocin”) is given by IV line and requires continuous electronic fetal monitoring. If labor does not start, the Pitocin can sometimes be stopped and restarted later if the bag of water is not broken and the mother and baby are healthy. Synthetic oxytocin is more likely to start labor than not trying to induce labor, and may be less likely to bring on labor than use of vaginal prostaglandins. Both methods have downsides.Alfirevic, Z., Kelly, A.J., & Dowswell, T. (2009). Intravenous oxytocin alone for cervical ripening and induction of labour. Cochrane Database of Systematic Reviews, 4.
- Pitocin and breaking the bag of water may be used together, and little is known about benefits and harms of this combination.Howarth, G. & Botha, D.J. (2001). Amniotomy plus intravenous oxytocin for induction of labour. Cochrane Database of Systematic Reviews, 3.
If the Bishop score is less than 6, most caregivers will recommend "cervical ripening" to make the cervix soft and ready to open. Three different methods may be used for this:
- Prostaglandin E2 (PGE2), a hormone medicine usually given as a gel, tablet or tampon inserted in the vagina.
- Misoprostol, a different hormone medicine. It comes in pill form and can be given by mouth or inserted in the vagina.
- Mechanical methods like a "Foley balloon," which is inserted through the cervix and then inflated so it puts pressure on the cervix from the inside.
Effectiveness and safety of these methods vary:Mozurkewich, E., Chilimigras, J.L., Berman, D.R., Perni, U.C., Romero, V.C., King, V.J., & Keeton, K.L. (2011). Methods of induction of labour: a systematic review. BMC Pregnancy and Childbirth, 11(84), 1-19.
- All of the methods increase the chance of having the baby within 24 hours.
- However, none of them reduces the chance of having a C-section, compared with inducing labor without these methods. (Misoprostol is a possible exception, but more research is needed.)
- PGE2 and misoprostol increase the chance of very strong contractions that can decrease oxygen flow to the baby.
- Misoprostol causes this problem more often than PGE2, but also works more quickly and may reduce the likelihood of having a C-section. Misoprostol should never be used in women planning a vaginal birth after cesarean (VBAC) because it increases the chance of uterine rupture.
- Mechanical methods like the Foley balloon are as effective as PGE2 and are less likely than both PGE2 and misoprostol to cause very strong contractions that can decrease oxygen to the baby.
- After cervical ripening, the woman will usually have Pitocin and the bag of water will be broken. However, sometimes cervical ripening methods work to induce labor on their own.
Scientists have begun to study new methods of inducing labor. These methods should not be used except in research studies, because they are still experimental:
- Isosorbide Mononitrate