OR WAIT 15 SECS
In 2014, 1.3 million women in the United States delivered via cesarean, placing the rate at 32.2%, down just .7% from the peak in 2009.
In 2014, 1.3 million women in the United States delivered via cesarean, placing the rate at 32.2%, down just .7% from the peak in 2009.1 That year, cesarean rates hit 32.9%, capping steady increases that started in 1996, when the rate was 20.7%.2 The rapid rise (a 50% increase over 13 years) came on the heels of a decline in the cesarean rate from 23.7% in 1987 to 20.8% in 1997- the only time in the past 3 decades that it fell in a developed country.3
The drop in the late 1980s and early 1990s was accomplished primarily because trials of labor after cesarean (TOLACs) had been rare and the rate of attempts rose to more than 40% in women with prior cesareans. Interestingly, the rise in TOLAC was accompanied by a slight decline in primary cesarean deliveries.4 In the 1990s, the increasing rates ran contrary to guidance from Healthy People 2010 (and then Healthy People 2020), which set a 15% goal for primary cesareans.5
The wide variation in cesarean rates among institutions is striking.6 The rate varies significantly even when controlling for characteristics that would account for indicated cesareans.7 The statistics are dramatic and concerning, leading to these key questions: Why is the cesarean rate rising, and is the rise influencing maternal or neonatal outcomes?
One possible reason for the rise in the cesarean delivery rate may be that there has simply been a rise in the need for cesarean. The most common indication for a primary cesarean is cephalo-pelvic disproportion, or arrest of progress in labor. It is unlikely that maternal pelvis size has changed over the past 3 decades, but it is possible that birth weight has increased. In fact, evidence suggests that rates of macrosomia have increased over the past 2 decades.8 Other issues that contribute to increasing rates of cesarean delivery, possibly through the mechanism of birth weight, are maternal obesity and gestational weight gain.9,10 Without question, the proportion of obese women has increased over the past decade and higher weight classes are associated with even higher rates of cesarean.11,12 In addition, increased gestational weight gain has been associated with cesarean delivery and is commonly above standard guidelines.13
Another reason for increasing cesarean rates may be a rise in elective cesarean delivery, also known as cesarean delivery by maternal request (CDMR). Because there was no ICD-9 code for CDMR, it is unclear what proportion of cesareans are due to it. One recent study, however, estimated the proportion as high as 4% in the United States.14 Interestingly, CDMR is more common in other countries, such as Brazil, Taiwan, and Chile. A study in Chile comparing women receiving private care (cesarean rate >40%) to women receiving public care (cesarean rate <20%) found that 8% of those receiving private care and 11% of those receiving public care stated a preference for cesarean delivery, with the vast majority preferring to deliver vaginally.15 Thus, even in this setting, it is unclear that maternal preferences are driving the increase in cesarean delivery rate.
The topic of CDMR led to a National Institutes of Health (NIH) state-of-the-science conference in 2006. The conclusion from this meeting was that future research was necessary to examine both the “current extent of CDMR and attitudes about it.”16 More recently, a study in the United States found that the vast majority of women would prefer to deliver vaginally.17
So, while some maternal demographics have changed and maternal preferences may account for a small proportion of cesarean deliveries, it appears that much of the rise in cesarean rates may be due to cultural pressures and norms. Some of these pressures are due to the medical-legal considerations that ob/gyns face. Physicians in one study reported that they were more likely to perform a cesarean in a number of scenarios if they had been sued recently or if they thought about being sued frequently.18 In another study, tort reform was associated with cesarean deliveries; in particular, overall cesarean rates were lower and vaginal birth after cesarean (VBAC) rates higher in states that had caps on noneconomic damage awards.19
Much is known about the effect of cesarean delivery on maternal and neonatal outcomes. Generally, there are positive and negative effects related to cesarean delivery on both mother and baby.20 Cesarean delivery has been associated with higher rates of maternal hemorrhage, infection, and even death but it is protective against perineal lacerations. 21,22 In turn, some evidence suggests that vaginal delivery may be associated with pelvic organ prolapse and fecal and urinary incontinence. Importantly, cesarean delivery has ramifications for future pregnancies, such as the risk of a TOLAC.23 In particular, the risk of abnormal placentation that can lead to a need for preterm delivery and cesarean hysterectomy, and the fact that it can be complicated by severe maternal hemorrhage, should receive significant attention when considering the risks of a cesarean delivery.24,25
Cesarean delivery is associated with lower rates of intrapartum hypoxic injury and neonatal mortality.26 With vaginal delivery, there is also always a risk of shoulder dystocia and permanent brachial plexus injury. Alternatively, neonates delivered via cesarean appear to experience higher rates of transient tachypnea and possibly primary pulmonary hypertension.11 Infants born to mothers who have had prior cesareans are at increased risk of stillbirth, and in cases of TOLAC, uterine rupture carries a risk to the neonate.27 For pregnancies complicated by abnormal placentation, delivery before term may be required.
The cesarean rate has risen without improving maternal or neonatal outcomes. The NIH, the American College of Obstetricians and Gynecologists (ACOG), and the Society for Maternal-Fetal Medicine (SMFM) convened a consensus conference 3 years ago on prevention of primary cesarean delivery. Approaches suggested at that meeting were published in a 2012 document.28 Further, a consensus statement cosponsored by ACOG and SMFM delineated the many approaches discussed here.29 When discussing lowering the cesarean rate, it is important to consider the most common indications for cesarean delivery, which are a prior cesarean, failed progression in labor, and abnormal fetal heart rate (FHR) tracing. Less common indications are malpresentation, multiple gestations, suspected fetal macrosomia, and herpes simplex virus.30
During the one period when cesarean rates fell in the United States, the focus was on TOLAC. Many hospitals and providers pushed back against attempting TOLAC, which led to a national VBAC rate of less than 10%. Although many women do not wish to bear the risk of a TOLAC, evidence suggests that more than 10% do, and that the current environment is restricting the wishes of many pregnant women with a prior cesarean. VBAC should likely not be universally available at every hospital in the country, but there are many hospitals where a safe TOLAC could be offered. Organizational changes in obstetric units such as having laborists available around the clock as well as availability of in-house anesthesia have improved the safety of a TOLAC, which remains a viable way to reduce the cesarean delivery rate overall.
Most indicated cesarean deliveries are performed for failed progression of labor during the first or second stage. These likely account for about a fifth of primary cesareans.28 Further, the majority of these primary cesareans will lead to future cesareans because of the low VBAC rate. The single most common indication is for failed progression in the first stage of labor, commonly diagnosed as “active phase arrest.” This diagnosis is based on labor norms established more than 50 years ago that have likely been relied on too absolutely.
In 1954, Emmanuel Friedman published a prospective analysis of labor norms drawn from a cohort of approximately 500 women.31 This study provided thresholds such as the fifth percentile of progression throughout labor that became universally utilized to ascertain when a labor was going too long.32 In Friedman’s work, the first stage of labor was divided into the latent and active phases, which were commonly demarcated by a cervical dilation of 3 to 4 cm. While during the latent phase, the labor could progress slowly, once the onset of active labor began, a progression of at least 1 cm of dilation per hour was anticipated. When progress was slower than this, a laboring woman could be said to be “falling off of the labor curve.” In this light, no progress for 2 hours was considered active phase arrest and became a common indication for a cesarean delivery.
More recent evidence, however, refutes use of these thresholds. The largest study reported that the 95th percentile of progress in labor from 4 to 5 cm is 6.4 hours and from 5 to 6 cm is 3.2 hours.33 This suggests that the active phase of labor may not begin until 6 cm of dilation in some women and a slow progression from 4 to 6 cm should be tolerated. Further, the 2-hour threshold has also been studied. 34 In a prospective study, researchers demonstrated that waiting for cervical change during the active phase of labor for at least 4 hours in the setting of adequate contractions or 6 hours without adequate contractions would lead to 60% of such women going on to deliver vaginally without evidence of harm to either the mother or the infant. In a similar study, investigators found not only a reduced cesarean rate and no evidence of increased neonatal morbidity but also reduced maternal risk.35
The amount of time beyond which a second stage of labor was characterized as prolonged was also likely too short. One important difference described recently is the additional time in the second stage in the setting of regional analgesia. Although an additional hour of the second stage has been traditionally utilized for women with an epidural, this appears to have been based on mean or median differences that are generally less than 1 hour. When a recent study examined the 95th percentile of differences between women without epidural in the second stage, a difference of 2 hours or more was identified in both nulliparous and multiparous women.36
Thus, management in the second stage should entail ongoing assessment of progress during the second stage, but should allow for at least 2 hours of second stage in multiparous women and 3 hours of second stage in nulliparous women, and an additional 2 hours in women with an epidural. In a recent small trial that randomized women to the additional hour in the second stage versus a more rapid delivery, the cesarean rate in the additional hour group was less than half that in the rapid delivery group (19.5% vs 43.2%, P<0.05).37 In addition, during the second stage, when the fetal vertex is engaged and has descended to a +2 station, operative vaginal delivery remains a beneficial adjunct to achieve vaginal delivery, although this has declined in recent years.37 It is important that the next generation of providers continue to be trained to perform operative vaginal deliveries.38
After abnormal progression in labor, the second-most-common indication for a cesarean during labor is an abnormal or indeterminate FHR tracing. Currently, FHR tracings are broken into categories 1, 2, and 3. Category 1 tracings are entirely benign and generally of no concern. Category 3 tracings are almost always an indication for immediate delivery and rarely controversial. The majority of FHR tracings, however, fall into category 2. In a recent study, more than 90% of FHR tracings were category 2 during the second stage of labor.39 Thus, category 2 tracings, are challenging and are not particularly predictive of neonatal acidemia.40 Although these have some features of concern such as FHR decelerations, category 2 tracings may have other reassuring features such as moderate variability.
Certainly, too many cesareans are performed for category 2 FHR tracings. Intervening steps should be taken before operative delivery. A range of resuscitative measures include maternal position change, intravenous fluids, and ensuring adequate blood pressure after obtaining regional analgesia. In addition, in the setting of repetitive FHR decelerations, if oxytocin augmentation is being utilized, it can be decreased or halted if there is concern.
Another approach for such repetitive decelerations has been the use of an intrauterine pressure catheter and amnioinfusion.41 Finally, if there is no moderate variability to reassure the clinician, fetal scalp stimulation with a response of FHR acceleration is useful to ensure a pH of more than 7.20.42
Augmention of FHR monitoring with use of ST segment analysis (STAN) was thought to have promise, but a recent trial did not find benefit from STAN technology.43 Although STAN and the previous fetal pulse oximetry trial did not show benefit over traditional FHR monitoring, improvement in baseline interpretation of FHR monitoring is still needed.44 Thus, close attention to the FHR pattern and recognition to ensure that there are only a few particularly concerning patterns will certainly prevent a number of cesareans. Despite the ubiquitous use of continuous FHR tracings for 40 years, ongoing clinical research is needed to ascertain the best use of this technology.
An additional management issue for patients in the second stage of labor is fetal malposition, particularly occiput transverse or occiput posterior position. Persistent fetal malposition occurs in approximately 5% of fetuses and is associated with an increased risk of cesarean delivery and both maternal and neonatal complications.45 One approach to malposition is patience. Similar to the epidural in the second stage of labor, fetal malposition will lead to longer first and second stages of labor. It is possible, however, that fetal malposition cannot be overcome simply by waiting. In such cases, rotation of the fetal occiput is useful. Historically, this was accomplished with forceps, particularly Kielland forceps. Because fewer ob/gyns are being trained to perform forceps rotations, however, manual rotation of the fetal occiput is more often attempted.46 This approach has been shown to significantly reduce the risk of cesarean delivery and is relatively safe and easy to teach.
Fetal malpresentation, most commonly breech presentation at term, is seen in approximately 4% of pregnancies.47 Currently, the vast majority of such pregnancies are delivered via cesarean. Thus, the primary approach to reducing cesareans in the setting of breech presentation is the use of external cephalic version (ECV). In general, ECV will be effective in approximately 70% of attempts and the majority of women with a successful ECV will go on to deliver vaginally.48 In addition, ECV success has been shown to be improved with the use of regional anesthesia; this concomitant approach should be more widely used.49 Finally, moxibustion (a Chinese medicine approach) has been shown to reduce breech presentation and should be mentioned to patients with a breech-presenting fetus.50
Supportive evidence exists for an attempt at vaginal delivery in the setting of a twin gestation if the presenting twin is cephalic. In particular, a recent
randomized trial found no improvement in neonatal outcomes in the setting of planned cesarean for a twin gestation.51 Thus, continued training of providers in vaginal delivery for both vertex–vertex and vertex–breech twins is imperative to allow this option for all women with twin gestations.
Interestingly, induction of labor has received a lot of negative attention as a source of cesarean deliveries. The evidence on this is not entirely clear, however. Although retrospective studies that compare induction and spontaneous labor do find such an association, this is an improper comparison. The true alternative to induction is expectant management (as opposed to spontaneous labor). When induction is compared to expectant management, it does not appear to be associated with an increase in the risk of cesarean delivery.52-54
In prospective randomized trials of women at 41 weeks’ gestation and beyond, the risk of cesarean delivery was lower in the women who were induced.55,56
Given this evidence, one might conclude that all women should be induced to prevent cesareans. That has not been demonstrated either, however. In fact, routine induction of labor in the wrong settings may increase the risk of cesarean delivery. In particular, using length of time to define a failed induction of labor can lead to an increase in cesareans.57
Thus, ACOG and SMFM’s consensus statement “Safe Prevention of the Primary Cesarean Delivery” suggested that no induction be called a failed induction until at least 24 hours of induction attempt or at least 12 to 18 hours after membrane rupture.29
Additionally, induction techniques should include cervical ripening agents (eg, prostaglandins, Foley bulb) in approaches to the unfavorable cervix.58
Another practice that may reduce the cesarean rate is continuous labor support.59 Whether the support person needs to have specific training or a longstanding relationship with the patient is less clear, but some institutions now have a doula pool for women who wish to have a doula but have not arranged for one prior to labor.
The exact mechanism of such support in reducing cesareans is unclear, but it appears to be an inexpensive way to avoid an operative delivery. Another approach is delayed admission in the latent phase of labor. Although there are no randomized trials, a recent study found the practice to reduce cesarean deliveries and costs.60
Although cesarean delivery may be a safe alternative to attempting vaginal delivery, its use in 1 in 3 women giving birth appears to be too high. Further, the effect of cesarean delivery on future pregnancies is likely not well considered when the first cesarean is being performed. Practices that have become standard over decades should be carefully questioned and replaced by standardized, evidence-based practices. This may safely decrease the cesarean rate.
Given the practice environment and cultural and medical-legal pressures that clinicians face, however, the healthcare system will need to adopt systems approaches to decrease the national cesarean delivery rate. Quality improvement and tort reform efforts will allow clinicians to adopt the range of practices described here. Without such environmental changes, however, clinicians may not be able to alter practice patterns that have been the norm for so long.
1. Hamilton BE, Martin JA, Osterman MJ, Curtain SC. Births: preliminary data for 2014. Natl Vital Stat Rep. 2015;64:1–19.
2. Menacker F, Hamilton BE. Recent trends in cesarean delivery in the United States. NCHS Data Brief.2010;35:1–8.
3. Declercq E, Young R, Cabral H, Ecker J. Is a rising cesarean delivery rate inevitable? Trends in industrialized countries, 1987 to 2007. Birth. 2011;38:99–104.
4. MacDorman M, Declercq E, Menacker F. Recent trends and patterns in cesarean and vaginal birth after cesarean (VBAC) deliveries in the United States. Clin Perinatol. 2011;38:179–192.
5. U.S. Department of Health and Human Services: Office of Disease Prevention and Health Promotion--Healthy People 2010. Nasnewsletter. 2000;15:3.
6. Kozhimannil KB, Law MR, Virnig BA. Cesarean delivery rates vary tenfold among US hospitals; reducing variation may address quality and cost issues. Health Aff (Millwood). 2013;32:527–535.
7. Kozhimannil KB, Arcaya MC, Subramanian SV. Maternal clinical diagnoses and hospital variation in the risk of cesarean delivery: analyses of a National US Hospital Discharge Database. PLoS Med. 2014;11:e1001745.
8. Stotland NE, Caughey AB, Breed EM, Escobar GJ. Risk factors and obstetric complications associated with macrosomia. Int J Gynaecol Obstet. 2004;87:220–226.
9. Weiss JL, Malone FD, Emig D, et al; FASTER Research Consortium. Obesity, obstetric complications and cesarean delivery rate-a population-based screening study. Am J Obstet Gynecol. 2004;190:1091–1097.
10. Stotland NE, Hopkins LM, Caughey AB. Gestational weight gain, macrosomia, and risk of cesarean birth in nondiabetic nulliparas. Obstet Gynecol. 2004;104:671–677.
11. Ogden CL, Carroll MD, Curtin LR, et al. Prevalence of overweight and obesity in the United States, 1999-2004. JAMA. 2006;295:1549–1555.
12. Marshall NE, Guild C, Cheng YW, et al. Maternal superobesity and perinatal outcomes. Am J Obstet Gynecol. 2012;206:417. e1–e6.
13. Swank ML, Caughey AB, Farinelli CK, et al. The impact of change in pregnancy body mass index on cesarean delivery. J Matern Fetal Neonatal Med. 2014;27:795–800.
14. Meikle SF, Steiner CA, Zhang J, Lawrence WL. A national estimate of the elective primary cesarean delivery rate. Obstet Gynecol. 2005;105:751–756.
15. Angeja A, Caughey AB, Vargas J, et al. Chilean women’s preferences regarding mode of delivery: which do they prefer and why? Obstet Gynecol. 2004;103:117S.
16. National Institutes of Health state-of-the-science conference statement: cesarean delivery on maternal request. March 27-29, 2006. Obstet Gynecol. 2006;107:1386–1397.
17. Sparks TN, Yeaton-Massey A, Granados JM, et al. Preference toward future mode of delivery: how do antepartum preferences and prior delivery experience contribute? J Matern Fetal Neonatal Med. 2015;28:1673–1678.
18. Cheng YW, Snowden JM, Handler SJ, et al. Litigation in obstetrics: does defensive medicine contribute to increases in cesarean delivery? J Matern Fetal Neonatal Med. 2014;27:1668–1675.
19. Yang YT, Mello MM, Subramanian SV, Studdert DM. Relationship between malpractice litigation pressure and rates of cesarean section and vaginal birth after cesarean section. Med Care. 2009;47:234–242.
20. Minkoff H, Chervenak FA. Elective primary cesarean delivery. N Engl J Med. 2003;348:946–950.
21. Harper MA, Byington RP, Espeland MA, et al. Pregnancy-related death and health care services. Obstet Gynecol. 2003;102:273–278.
22. Handa VL, Harris TA, Ostergard DR. Protecting the pelvic floor: obstetric management to prevent incontinence and pelvic organ prolapse. Obstet Gynecol. 1996;88:470–478.
23. Landon MB, Hauth JC, Leveno KJ, et al; National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. Maternal and perinatal outcomes associated with a trial of labor after prior cesarean delivery. N Engl J Med. 2004;351:2581–2589.
24. Silver RM, Landon MB, Rouse DJ, et al; National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. Maternal morbidity associated with multiple repeat cesarean deliveries. Obstet Gynecol. 2006;107:1226–1232.
25. Solheim KN, Esakoff TF, Little SE, et al. The effect of current cesarean delivery rates on the future incidence of placenta previa, placenta accreta, and maternal mortality. J Matern Fetal Neonatal Med. 2011;24:1341–1346.
26. Smith GC, Pell JP, Cameron AD, Dobbie R. Risk of perinatal death associated with labor after previous cesarean delivery in uncomplicated term pregnancies. JAMA. 2002;287:2684–2690.
27. Smith GC, Pell JP, Dobbie R. Caesarean section and risk of unexplained stillbirth in subsequent pregnancy. Lancet. 2003;362:1779–1784.
28. Spong CY, Berghella V, Wenstrom KD, et al. Preventing the first cesarean delivery: summary of a joint Eunice Kennedy Shriver National Institute of Child Health and Human Development, Society for Maternal-Fetal Medicine, and American College of Obstetricians and Gynecologists Workshop. Obstet Gynecol. 2012;120:1181–1193.
29. American College of Obstetricians and Gynecologists; Society for Maternal-Fetal
Medicine. Obstetric care consensus no. 1: safe prevention of the primary cesarean delivery. Obstet Gynecol. 2014;123:693–711.
30. Barber EL, Lundsberg LS, Belanger K, et al. Indications contributing to the increasing cesarean delivery rate. Obstet Gynecol. 2011;118:29–38.
31. Friedman E. The graphic analysis of labor. Am J Obstet Gynecol. 1954;68:1568–1575.
32. Friedman EA. An objective approach to the diagnosis and management of abnormal labor. Bull N Y Acad Med. 1972;48:842–858.
33. Zhang J, Landy HJ, Branch DW, et al; Consortium on Safe Labor. Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol. 2010;116:1281–1287.
34. Rouse DJ, Owen J, Savage KG, Hauth JC. Active phase labor arrest: revisiting the 2-hour minimum. Obstet Gynecol. 2001;98:550–554.
35. Henry DE, Cheng YW, Shaffer BL, et al. Perinatal outcomes in the setting of active phase arrest of labor. Obstet Gynecol. 2008;112:1109–1115.
36. Cheng YW, Shaffer BL, Nicholson JM, Caughey AB. Second stage of labor and epidural use: a larger effect than previously suggested. Obstet Gynecol. 2014;123:527–535.
37. Gimovsky AC, Berghella V. Randomized controlled trial of prolonged second stage: extending the time limit vs usual guidelines. Am J Obstet Gynecol. 2016 Mar;214(3):361.e1-6.
38. Srinivas SK, Epstein AJ, Nicholson S, et al. Improvements in US maternal obstetrical outcomes from 1992 to 2006. Med Care. 2010;48:487–493.
38. Shaffer BL, Caughey AB. Forceps delivery: potential benefits and a call for continued training. J Perinatol. 2007;27:327–328.
39. Cahill AG, Roehl KA, Odibo AO, Macones GA. Association and prediction of neonatal acidemia. Am J Obstet Gynecol. 2012;207:206.e1–e8.
40. Cahill AG, Roehl KA, Odibo AO, Macones GA. Association of atypical decelerations with acidemia. Obstet Gynecol. 2012;120:1387–1393.
41. Macri CJ, Schrimmer DB, Leung A, et al. Prophylactic amnioinfusion improves outcome of pregnancy complicated by thick meconium and oligohydramnios. Am J Obstet Gynecol. 1992;167:117–121.
42. Elimian A, Figueroa R, Tejani N. Intrapartum assessment of fetal well-being: a comparison of scalp stimulation with scalp blood pH sampling. Obstet Gynecol. 1997;89:373–376.
43. Belfort MA, Saade GR, Thom E, et al; Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal–Fetal Medicine Units Network. A randomized trial of intrapartum fetal ECG ST-segment analysis. N Engl J Med. 2015;373:632–641.
44. Bloom SL, Spong CY, Thom E, et al. Fetalpulse oximetry and cesarean delivery. N Engl J Med. 2006;355:2195–2202.
45. Cheng YW, Hubbard A, Caughey AB, Tager IB. The association between persistent fetal occiput posterior position and perinatal outcomes: an example of propensity score and covariate distance matching. Am J Epidemiol. 2010;171:656–663.
46. Shaffer BL, Cheng YW, Vargas JE, Caughey AB. Manual rotation to reduce caesarean delivery in persistent occiput posterior or transverse position. J Matern Fetal Neonatal Med. 2011;24:65–72.
47. Lee HC, El-Sayed YY, Gould JB. Population trends in cesarean delivery for breech presentation in the United States, 1997-2003. Am J Obstet Gynecol. 2008;199:59.e1–e8.
48. Clock C, Kurtzman J, White J, Chung JH. Cesarean risk after successful external cephalic version: a matched, retrospective analysis. J Perinatol. 2009;29:96–100.
49. Yoshida M, Matsuda H, Kawakami Y, et al. Effectiveness of epidural anesthesia for external cephalic version (ECV). J Perinatol. 2010;30:580–583.
50. Cardini F, Weixin H. Moxibustion for correction of breech presentation: a randomized controlled trial. JAMA. 1998;280:1580–1584.
51. Barrett JF, Hannah ME, Hutton EK, et al; Twin Birth Study Collaborative Group.A randomized trial of planned cesarean or vaginal delivery for twin pregnancy. N Engl J Med. 2013;369:1295–1305.
52. Caughey AB, Nicholson JM, Cheng YW, et al. Induction of labor and cesarean delivery by gestational age. Am J Obstet Gynecol. 2006;195:700–705.
53. Darney BG, Snowden JM, Cheng YW, et al. Elective induction of labor at term compared with expectant management: maternal and neonatal outcomes. Obstet Gynecol. 2013;122:761–769.
54. Stock SJ, Ferguson E, Duffy A, et al. Outcomes of elective induction of labour compared with expectant management: population based study. BMJ. 2012;344:e2838.
55. Gülmezoglu AM, Crowther CA, Middleton P, Heatley E. Induction of labour for improving birth outcomes for women at or beyond term. Cochrane Database Syst Rev. 2012;6:CD004945.
56. Caughey AB, Sundaram V, Kaimal AJ, et al. Systematic review: elective induction of labor versus expectant management of pregnancy. Ann Intern Med. 2009;151:252–263.
57. Rouse DJ, Owen J, Hauth JC. Criteria for failed labor induction: prospective evaluation of a standardized protocol. Obstet Gynecol. 2000;96:671–677.
58. Wing DA, Sheibani L. Pharmacotherapy options for labor induction. Expert Opin Pharmacother. 2015;16:1657–1668.
59. Hodnett ED, Gates S, Hofmeyr GJ, Sakala C. Continuous support for women during childbirth. Cochrane Database Syst Rev. 2012;10:CD003766.
60. Tilden EL, Lee VR, Allen AJ, et al. Cost-effectiveness analysis of latent versus active labor hospital admission for medically low-risk, term women. Birth. 2015;42:219–226.