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Induction of labor versus expectant management for women with a prior cesarean delivery
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Induction of labor versus expectant management for women with a prior cesarean delivery Anna Palatnik, MD; William A. Grobman, MD, MBA OBJECTIVE: Previous studies of induction of labor in the setting of trial of labor after cesarean have compared women undergoing trial of labor after cesarean to those undergoing spontaneous labor. However, the clinically relevant comparison is to those undergoing expectant management. The objective of this study was to compare obstetric outcomes between women undergoing induction of labor and those undergoing expectant management 39 weeks of gestation. STUDY DESIGN: This was a secondary analysis of data from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network Cesarean Registry that included women with singleton gestations at a gestational age of 39 weeks and a history of 1 low transverse cesarean delivery. Outcomes of induction at 39, 40, and 41 weeks were compared to expectant management beyond each gestational age period using univariable and multivariable analyses. Women with scheduled repeat cesarean deliveries done for the indication of prior cesarean delivery were excluded from the analysis.
RESULTS: In all, 12,676 women were eligible for analysis. The rate of vaginal birth after cesarean (VBAC) was higher among women undergoing induction of labor at 39 weeks compared to expectant management (73.8% vs 61.3%, P < .001). The risk of uterine rupture also was higher among women undergoing induction of labor at 39 weeks compared to expectant management (1.4% vs 0.5%, P ¼ .006, respectively). In multivariable analysis, induction of labor at 39 weeks remained associated with a significantly higher chance of VBAC and uterine rupture (odds ratio, 1.31; 95% confidence interval, 1.03e1.67; and odds ratio, 2.73; 95% confidence interval, 1.22e6.12, respectively). CONCLUSION: Induction of labor at 39 weeks, when compared to
expectant management, was associated with a higher chance of VBAC but also of uterine rupture. Key words: induction of labor, uterine rupture, vaginal birth after cesarean delivery
Cite this article as: Palatnik A, Grobman WA. Induction of labor versus expectant management for women with a prior cesarean delivery. Am J Obstet Gynecol 2015;212:358.e1-6.
I
t is commonly believed that women with a prior cesarean delivery who undergo induction of labor are less likely to have vaginal birth after cesarean (VBAC).1 Indeed, observational studies have consistently shown that women who are induced after a prior cesarean have a 15-20% higher chance of cesarean delivery.2-7 In addition, several studies have shown that induction of labor is associated with an approximately 2-fold increased risk of uterine rupture.8-11
However, these conclusions are from comparisons with women who were in spontaneous labor. Caughey et al12 and others13,14 have demonstrated how this comparison group is not clinically relevant, because the actual alternative to induction is not spontaneous labor but expectant management. In fact, among women without a prior cesarean delivery, when labor induction has been
From the Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, IL. Received Oct. 18, 2014; revised Dec. 17, 2014; accepted Jan. 19, 2015. The authors report no conflict of interest. Presented in oral format at the 35th annual meeting of the Society for Maternal-Fetal Medicine, San Diego, CA, Feb. 2-7, 2015. The racing flag logo above indicates that this article was rushed to press for the benefit of the scientific community. Corresponding author: Anna Palatnik, MD. [email protected] 0002-9378/free ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajog.2015.01.026
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compared to expectant management instead of spontaneous labor, metaanalysis of observational studies has revealed a lower chance of cesarean delivery among those who were induced.15 The consequences of labor induction compared to expectant management among women with a prior cesarean remain uncertain. We hypothesized that induction of labor 390/7 weeks of gestation would not be associated with an increased chance of cesarean when compared to expectant management among women planning trial of labor after cesarean. We also investigated whether labor induction is associated with an increase in the risk of uterine rupture or other obstetric morbidities.
M ATERIALS
AND
M ETHODS
This was a secondary analysis of data from the Cesarean Registry of the Eunice
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TABLE 1
Characteristics of women undergoing induction of labor with 1 prior cesarean delivery compared to expectant management IOL
EM
39 e39 wk (n [ 638) 0/7
Characteristic
3/7
IOL
>39 wk (n [ 7565) 3/7
EM
40 e40 wk (n [ 522) 0/7
3/7
IOL
>40 wk (n [ 2933) 3/7
EM
41 e41 wk (n [ 471) 0/7
3/7
>413/7 wk (n [ 547)
Age, y
30.2 5.4b
28.1 5.7
29.7 5.4b
27.7 5.7
28.7 5.5b
27.4 5.6
Prepregnancy BMI
27.0 6.6
26.7 6.3
27.3 6.7
27.0 6.4
27.6 7.3
27.3 6.1
Race African American Caucasian Hispanic Other Cigarette use during
157 (24.6)b 391 (61.3) 55 (8.6)
b
35 (5.5)
b
b
2556 (33.8)
159 (30.4)b
1066 (36.3)
157 (33.3)b
220 (40.2)
2116 (27.9)
b
733 (25.0)
188 (39.9)b
104 (19.0)
973 (33.2)
b
191 (34.9)
2473 (32.7)
75 (11.7)
263 (50.4)
b
69 (13.2) b
421 (5.6)
30 (5.7)
971 (12.8)
69 (13.2)
3228 (42.9)
238 (46.1)
94 (20.0) b
160 (5.4)
32 (6.8)
32 (5.8)
395 (13.5)
67 (14.2)
1270 (43.6)
188 (39.9)b
255 (47.0)
777 (26.5)
117 (24.8)
153 (28.0)
96 (17.6)
Pregnancy Prior vaginal delivery
362 (56.8)b
Prior VBAC
254 (39.8)
b
b
2010 (26.5)
169 (32.4)
Recurrent indication for prior
173 (27.1)b
2475 (39.8)
169 (32.4)
937 (38.5)
145 (30.8)
193 (40.2)
9 (1.4)
63 (0.8)
6 (1.1)
17 (0.6)
4 (0.8)
5 (0.9)
CD Chronic medical illnessa All data presented as mean SD or N (%). BMI, body mass index; CD, cesarean delivery; EM, expectant management; IOL, induction of labor; VBAC, vaginal birth after cesarean. a
Includes chronic hypertension, pregestational diabetes, asthma, seizure disorder, thyroid disease, or renal insufficiency; b P < .05 for comparison of labor induction vs EM at given gestational age.
Palatnik. Induction of labor after prior cesarean delivery. Am J Obstet Gynecol 2015.
Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. That registry was the result of a 4eyear multicenter observational study, designed to address clinical issues related to cesarean childbirth.8 In the present analysis, we included all women from the registry who had a history of 1 cesarean delivery via a low transverse or unknown uterine incision and were at a gestational age of at least 390/7 weeks. Women with scheduled repeat cesarean deliveries done for the indication of prior cesarean delivery were excluded from the analysis. Women who underwent labor induction were divided into 3 comparison groups based on the timing of their induction of labor: 390/7-393/7, 400/7-403/7, and 410/7-413/7 weeks. Gestational age was based on the best obstetric estimate (last menstrual period compared with ultrasonography), determined by health care providers and used for clinical
decision-making.8 Women who underwent induction during each gestational age window were compared with women who were managed expectantly after the same gestational age window. This design was used to mimic the prospective choice of undertaking a labor induction during a given period of time at the start of a given week of gestation or undergoing expectant management from that time forward. In an effort to evaluate women who were not in need of immediate delivery due to the onset of an acute obstetric complication, women were excluded from the induction group when they had an acute obstetric medical indication for induction (ie, preeclampsia, gestational hypertension, nonreassuring antenatal surveillance, oligohydramnios, fetal growth restriction, and antenatal intrauterine fetal demise). However, if women developed these conditions while they were being expectantly managed, they were not
excluded from the expectant management group, as 1 consequence of expectant management is that these conditions may develop and require delivery. A recurrent indication for cesarean delivery was defined as a cesarean due to any type of arrest disorder. Uterine rupture was defined as a disruption or tear of the uterine muscle and visceral peritoneum or a separation of the uterine muscle with extension to the bladder or broad ligament. To ensure that our results were not solely dependent upon our primary analytic approach and group composition, we performed additional analyses in which the inclusion criteria for the group of women expectantly managed was altered slightly. In 1 analysis, we included women who underwent labor from the first day at which women also may have undergone labor induction (ie, laboring women were included in the
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expectantly managed group from 390/7 weeks, instead of only from 394/7 weeks as in the primary analysis). In another analysis, we included women in the expectant management group if they remained pregnant at least 1 week longer than the first day women underwent labor induction in the comparison group but then underwent a scheduled repeat cesarean with prior cesarean as the primary indication, given it is possible that these women initially may have chosen expectant management (instead of planned cesarean) but then decided to forego trial of labor after cesarean when they had not labored by a given gestational age. All analyses were performed with software (Stata, version 12.0; StataCorp, College Station, TX). Univariable comparisons of maternal and neonatal characteristics and pregnancy outcomes were performed using Pearson c2 test and Fisher exact test for categorical data and the Student t test for continuous measures. Additionally, multivariable logistic regression was performed for the outcomes that were significantly different in univariable analysis. Potential confounding variables were entered
into the regression equation if they differed between groups in univariable analysis at a level of P < .05. Odds ratios with 95% confidence intervals were estimated from the logistic regression. This study was considered exempt by the Northwestern University Institutional Review Board because only de-identified data were used.
not reach statistical significance. Women induced at 390/7-393/7 weeks also had a higher chance of uterine rupture compared to women managed expectantly beyond that gestational age (Table 2). There were no other differences in obstetric morbidity between women who were induced and who were expectantly managed. Neonatal characteristics and outcomes are depicted in Table 3. Neonates of women who were induced at 390/7393/7 and 400/7-403/7 weeks had lower birthweight compared to neonates whose mothers were managed expectantly (P < .001 and P ¼ .03, respectively). Overall, neonatal outcomes at each gestational age did not differ significantly among the comparison groups. The point estimates of the frequencies of neonatal intensive care unit admission, hypoxic-ischemic encephalopathy, and perinatal death were higher among neonates whose mothers were in the expectant management groups, however these differences did not reach statistical significance (Table 3). Multivariable analyses for the likelihood of VBAC and uterine rupture are presented in Table 4. Induction of labor
R ESULTS In all, 12,676 women were eligible for analysis. Maternal characteristics of the study population according to the gestational age at which they underwent labor induction or expectant management are depicted in Table 1. Women undergoing induction of labor differed in several ways from those who were expectantly managed, including in their age, race, and obstetric history. Maternal outcomes are depicted in Table 2. Women induced at 390/7-393/7 weeks compared to those who were managed expectantly had higher rates of VBAC. A higher chance of VBAC similarly was noted among women who were induced at 400/7-403/7 weeks, compared to those expectantly managed beyond that gestational age, but the results did
TABLE 2
Outcomes of women undergoing induction of labor after 1 prior cesarean delivery compared to expectant management IOL
EM
IOL
EM
IOL
EM
Maternal outcome
39 e39 wk (n [ 638)
>39 wk (n [ 7565 )
40 e40 wk (n [ 522)
>40 wk (n [ 2933)
41 e41 wk (n [ 471)
>413/7 wk (n [ 547)
VBAC
471 (73.8)b
4640 (61.3)
340 (65.1)
1817 (61.9)
277 (58.8)
330 (60.3)
Third/fourth degree
28 (4.4)
311 (4.1)
30 (5.7)
108 (3.7)
27 (5.7)
14 (2.5)
Endometritis
13 (2.0)
255 (3.4)
12 (2.3)
115 (3.9)
20 (4.2)
16 (2.9)
4 (0.6)
29 (0.4)
4 (0.7)
12 (0.4)
1 (0.2)
2 (0.3)
6 (0.9)
122 (1.6)
14 (2.7)
45 (1.5)
9 (1.9)
11 (2.0)
22 (0.3)
4 (0.7)
10 (0.3)
0
0/7
Wound complication Blood transfusion Operative complications
a
3/7
1 (0.1) b
3/7
0/7
3/7
3/7
0/7
3/7
1 (0.2)
Uterine rupture
9 (1.4)
40 (0.5)
7 (1.3)
17 (0.6)
6 (1.3)
2 (0.4)
Hysterectomy
0
11 (0.1)
3 (0.6)
5 (0.2)
0
3 (0.5)
ICU admission
1 (0.1)
21 (0.3)
3 (0.6)
7 (0.2)
0
1 (0.2)
Maternal death
0
1 (0.2)
0
0
0
1 (0.01)
All data presented as mean SD or N (%). EM, expectant management; ICU, intensive care unit; IOL, induction of labor; VBAC, vaginal birth after cesarean. a
Cystotomy, ureteral injury, bowel injury; b P < .05 for comparison of labor induction vs EM at given gestational age.
Palatnik. Induction of labor after prior cesarean delivery. Am J Obstet Gynecol 2015.
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TABLE 3
Neonatal outcomes of women undergoing induction of labor after 1 prior cesarean delivery compared to expectant management IOL
EM
39 e39 wk (n [ 638) 0/7
Variable Male
3/7
309 (48.4)
Birthweight, g
3416 448
b
5-min Apgar score 5 Umbilical artery pH 7.0 Admission to NICU
2 (0.3)
IOL
>39 wk (n [ 7565 ) 3/7
46 (7.2)
40 e40 wk (n [ 522) 3/7
3805 (50.3)
271 (51.9)
3527 461
3543 443
60 (0.8)
5/183 (2.7)
EM
0/7
b
>40 wk (n [ 2933)
703 (9.3)
5/169 (2.9) 48 (9.2)
EM
41 e41 wk (n [ 471) 0/7
3/7
>413/7 wk (n [ 547)
1517 (51.7)
241 (51.2)
285 (52.1)
3591 466
3645 428
3600 493
4 (0.8)
58/3445 (1.7)
IOL 3/7
24 (0.8) 30/1417 (2.1)
2 (0.4)
8 (1.4)
3/172 (1.7)
6/294 (2.0)
39 (8.3)
64 (11.7)
309 (10.5)
Antepartum or intrapartum death
0
9 (0.1)
0
4 (0.1)
0
4 (0.7)
Hypoxic-ischemic Encephalopathy
0
5 (0.06)
1 (0.2)
2 (0.07)
0
1 (0.2)
Neonatal death
0
3 (0.04)
0
1 (0.03)
0
0
Perinatal deatha
0
0
5 (0.2)
0
4 (0.7)
12 (0.1)
All data presented as mean SD or N (%). EM, expectant management; IOL, induction of labor; NICU, neonatal intensive care unit; VBAC, vaginal birth after cesarean. a
Antepartum, intrapartum, or neonatal death; b P < .05 for comparison of labor induction vs EM at given gestational age.
Palatnik. Induction of labor after prior cesarean delivery. Am J Obstet Gynecol 2015.
at 390/7-393/7 weeks continued to be associated with a significantly higher chance of VBAC compared to expectant management. Although induction of labor at later gestational ages also was associated with higher odds of VBAC, this difference did not reach statistical significance. Similarly, in the
multivariable analysis, induction of labor at 390/7-393/7 weeks compared to expectant management was associated with a higher risk of uterine rupture; this association did not reach statistical significance when labor inductions were compared to expectant management at later gestational ages. Results did not
TABLE 4
Association of labor induction with VBAC and uterine rupture compared to expectant management OR
95% CI
aORa
95% CI
390/7e393/7
1.78
1.48e2.13
1.31
1.03e1.67
40 e40
3/7
1.15
0.94e1.39
1.21
0.93e1.56
41 e41
3/7
0.94
0.73e1.21
1.04
0.76e1.43
390/7e393/7
2.69
1.30e5.57
2.73
1.22e6.12
40 e40
3/7
2.33
0.96e5.65
2.31
0.84e6.33
41 e41
3/7
3.52
0.71e17.50
3.13
0.58e16.88
Gestational age at IOL, wk VBAC 0/7 0/7
Risk of uterine rupture 0/7 0/7
aOR, adjusted odds ratio; CI, confidence interval; IOL, induction of labor; OR, odds ratio; VBAC, vaginal birth after cesarean. a
Adjusted for maternal age, race, recurrent indication for prior cesarean delivery, presence of prior vaginal delivery, and presence of prior VBAC.
Palatnik. Induction of labor after prior cesarean delivery. Am J Obstet Gynecol 2015.
differ for the analyses that used different inclusion criteria to construct the expectant management group.
C OMMENT In this secondary analysis we sought to evaluate outcomes in women who were at least 390/7 weeks of gestation with 1 prior cesarean delivery and who underwent induction of labor vs expectant management. We found that the rates of both VBAC and uterine rupture were higher among women undergoing induction of labor at 390/7-393/7 weeks compared to those undergoing expectant management. A similar pattern in these outcomes was seen with induction of labor at later gestational ages, although the differences did not reach statistical significance, perhaps because of lesser power associated with a smaller sample size. Other maternal and neonatal outcomes were similar between the 2 groups. The results of this study in regard to VBAC are in contrast to the results of those studies that have compared labor induction with spontaneous labor. These cohort studies of nulliparous women described approximately a 2-fold increased risk of cesarean delivery with
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induction of labor.6,7,16-18 However, as has been noted by others, to evaluate outcomes associated with labor induction in an actual clinical context, the relevant clinical comparison is between labor induction and expectant management.12-14 When this comparison has been made among women without a prior cesarean, induction of labor 39 weeks actually has been associated with a lower chance of cesarean.14,19-22 One group of investigators who evaluated women with a prior cesarean also found that labor induction was associated with a lower chance of cesarean.23 This study additionally suggested that there was no difference in the risk of uterine rupture associated with labor induction or perinatal mortality, although there was a significant increase in the frequency of neonatal intensive care unit admission and postpartum hemorrhage among women who underwent labor induction at some gestational ages. However, the data source used was an administrative database collected over >3 decades; such a data source may be prone to multiple biases.24 In contrast, our study used a database derived from direct chart abstraction by trained research nurses. Nevertheless, our results that labor induction was associated with a lower chance of repeat cesarean and a greater chance of VBAC are similar to those of Stock et al.23 In contrast, our result with regard to the association between labor induction and uterine rupture is not consistent with that of Stock et al,23 but is consistent with other observational studies, even if those studies used spontaneous labor as the comparison group.3,9-10 A recent metaanalysis comparing induction and spontaneous labor after prior cesarean showed 1.6-fold increase in the incidence of uterine rupture with induction (95% confidence interval, 1.13e2.31).25 Similarly, in this study, the odds of uterine rupture in the context of labor induction were approximately doubled, although the attributable risk increase was <1%. The limitations of this analysis should be noted. First, we did not know the cervical examination at the time expectant management was pursued and thus
could not account for cervical status in stratified or regression analysis. This inability could potentially bias our results if, for example, women who were managed expectantly were more likely to have unfavorable cervices compared to those who were induced. Another limitation is the fixed sample size of the overall cohort. Although our comparison of maternal and neonatal outcomes did not reach statistical significance among women at 400/7 weeks of gestation, it is possible that this is due to the relatively smaller size of these subgroups and a corresponding reduction in the power to detect a difference. There also could be other unmeasured differences between the groups that could explain the observed associations. Lastly, because of its observational nature we cannot know that a prospective policy of labor induction, either electively or for particular medical indications, would result in the same outcomes. Labor induction for women with a prior cesarean delivery is considered acceptable practice by the American Congress of Obstetricians and Gynecologists.1 Nevertheless, the final determination of whether a labor induction should be undertaken needs to be made by a woman, informed of the risks and benefits, who is working with her physician to ascertain her most preferred approach to delivery based on her individual circumstances. The results of this study can help provide guidance to women and their providers during this decisionmaking process. ACKNOWLEDGMENT We would like to acknowledge the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the Maternal-Fetal Medicine Units Network, and the Protocol Subcommittee for making this database publically available.
REFERENCES 1. American College of Obstetricians and Gynecologists. Vaginal birth after previous cesarean delivery. ACOG Practice bulletin no. 115. Obstet Gynecol 2010;116:450-63. 2. Macones GA, Hausman N, Edelstein R, Stamilio DM, Marder SJ. Predicting outcomes of trials of labor in women attempting vaginal birth
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after cesarean delivery: a comparison of multivariate methods with neural networks. Am J Obstet Gynecol 2001;184:409-13. 3. Sims EJ, Newman RB, Hulsey TC. Vaginal birth after cesarean: to induce or not to induce. Am J Obstet Gynecol 2001;184: 1122-4. 4. Landon MB, Leindecker S, Spong CY, et al. The MFMU cesarean registry: factors affecting the success of trial of labor after previous cesarean delivery. Am J Obstet Gynecol 2005;193: 1016-23. 5. Delaney T, Young DC. Spontaneous versus induced labor after a previous cesarean delivery. Obstet Gynecol 2003;102:39-44. 6. Luthy DA, Malmgren JA, Zingheim RW. Cesarean delivery after elective induction in nulliparous women: the physician effect. Am J Obstet Gynecol 2004;191:1511-5. 7. Hoffman MK, Vahratian A, Sciscione AC, Troendle JF, Zhang J. Comparison of labor progression between induced and noninduced multiparous women. Obstet Gynecol 2006;107: 1029-34. 8. 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: 2581-9. 9. Macones GA, Peipert J, Nelson DB, et al. Maternal complications with vaginal birth after cesarean delivery: a multicenter study. Am J Obstet Gynecol 2005;193:1656-62. 10. Lydon-Rochelle M, Holt VL, Easterling TR, Martin DP. Risk of uterine rupture during labor among women with a prior cesarean delivery. N Engl J Med 2001;345:3-8. 11. Grobman WA, Lai Y, Landon MB, et al. Prediction of uterine rupture associated with attempted vaginal birth after cesarean delivery. Am J Obstet Gynecol 2008;199:30. e1-5. 12. Caughey AB, Nicholson JM, Cheng YW, Lyell DJ, Washington AE. Induction of labor and cesarean delivery by gestational age. Am J Obstet Gynecol 2006;195:700-5. 13. Osmundson S, Ou-Yang RJ, Grobman WA. Elective induction compared with expectant management in nulliparous women with an unfavorable cervix. Obstet Gynecol 2011;117: 583-7. 14. Stock SJ, Ferguson E, Duffy A, Ford I, Chalmers J, Norman JE. Outcomes of elective induction of labor compared with expectant management: population-based study. BMJ 2012;344:e2838. 15. Mishanina E, Rogozinska E, Thatthi T, Uddin-Khan R, Khan KS, Meads C. Use of labor induction and risk of cesarean delivery: a systematic review and meta-analysis. CMAJ 2014;186:665-73. 16. Seyb ST, Berka RJ, Socol ML, Dooley SL. Risk of cesarean delivery with elective induction of labor at term in nulliparous women. Obstet Gynecol 1999;94:600-7.
ajog.org 17. Yeast JD, Jones A, Poskin M. Induction of labor and the relationship to cesarean delivery: a review of 7001 consecutive inductions. Am J Obstet Gynecol 1999;180:628-33. 18. Smith KM, Hoffman MK, Sciscione A. Elective induction of labor in nulliparous women increases the risk of cesarean delivery. Obstet Gynecol 2003;101:45S. 19. Cheng YW, Kaimal AJ, Snowden JM, Nicholson JM, Caughey AB. Induction of labor compared to expectant management in low-risk women and associated perinatal outcomes. Am J Obstet Gynecol 2012;207: 502.e1-8.
Obstetrics 20. Gülmezoglu AM, Crowther CA, Middleton P, Heatley E. Induction of labor for improving birth outcomes for women at or beyond term. Cochrane Database Syst Rev 2012;6: CD004945. 21. 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: 761-9. 22. Gibson KS, Waters TP, Bailit JL. Maternal and neonatal outcomes in electively induced low-risk term pregnancies. Am J Obstet Gynecol 2014;211:249.e1-16.
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23. Stock SJ, Ferguson E, Duffy A, Ford I, Chalmers J, Norman JE. Outcomes of induction of labor in women with previous cesarean delivery: a retrospective cohort study using a population database. PLoS One 2013;8: e60404. 24. Grimes DA. Epidemiologic research using administrative databases: garbage in, garbage out. Obstet Gynecol 2010;116:1018-9. 25. Rossi AC, Prefumo F. Pregnancy outcomes of induced labor in women with previous cesarean section: a systematic review and metaanalysis. Arch Gynecol Obstet 2015;291: 273-80.
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OBSTETRICS
Induction of labor versus expectant management for women with a prior cesarean delivery Anna Palatnik, MD; William A. Grobman, MD, MBA OBJECTIVE: Previous studies of induction of labor in the setting of trial of labor after cesarean have compared women undergoing trial of labor after cesarean to those undergoing spontaneous labor. However, the clinically relevant comparison is to those undergoing expectant management. The objective of this study was to compare obstetric outcomes between women undergoing induction of labor and those undergoing expectant management 39 weeks of gestation. STUDY DESIGN: This was a secondary analysis of data from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network Cesarean Registry that included women with singleton gestations at a gestational age of 39 weeks and a history of 1 low transverse cesarean delivery. Outcomes of induction at 39, 40, and 41 weeks were compared to expectant management beyond each gestational age period using univariable and multivariable analyses. Women with scheduled repeat cesarean deliveries done for the indication of prior cesarean delivery were excluded from the analysis.
RESULTS: In all, 12,676 women were eligible for analysis. The rate of vaginal birth after cesarean (VBAC) was higher among women undergoing induction of labor at 39 weeks compared to expectant management (73.8% vs 61.3%, P < .001). The risk of uterine rupture also was higher among women undergoing induction of labor at 39 weeks compared to expectant management (1.4% vs 0.5%, P ¼ .006, respectively). In multivariable analysis, induction of labor at 39 weeks remained associated with a significantly higher chance of VBAC and uterine rupture (odds ratio, 1.31; 95% confidence interval, 1.03e1.67; and odds ratio, 2.73; 95% confidence interval, 1.22e6.12, respectively). CONCLUSION: Induction of labor at 39 weeks, when compared to
expectant management, was associated with a higher chance of VBAC but also of uterine rupture. Key words: induction of labor, uterine rupture, vaginal birth after cesarean delivery
Cite this article as: Palatnik A, Grobman WA. Induction of labor versus expectant management for women with a prior cesarean delivery. Am J Obstet Gynecol 2015;212:358.e1-6.
I
t is commonly believed that women with a prior cesarean delivery who undergo induction of labor are less likely to have vaginal birth after cesarean (VBAC).1 Indeed, observational studies have consistently shown that women who are induced after a prior cesarean have a 15-20% higher chance of cesarean delivery.2-7 In addition, several studies have shown that induction of labor is associated with an approximately 2-fold increased risk of uterine rupture.8-11
However, these conclusions are from comparisons with women who were in spontaneous labor. Caughey et al12 and others13,14 have demonstrated how this comparison group is not clinically relevant, because the actual alternative to induction is not spontaneous labor but expectant management. In fact, among women without a prior cesarean delivery, when labor induction has been
From the Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, IL. Received Oct. 18, 2014; revised Dec. 17, 2014; accepted Jan. 19, 2015. The authors report no conflict of interest. Presented in oral format at the 35th annual meeting of the Society for Maternal-Fetal Medicine, San Diego, CA, Feb. 2-7, 2015. The racing flag logo above indicates that this article was rushed to press for the benefit of the scientific community. Corresponding author: Anna Palatnik, MD. [email protected] 0002-9378/free ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajog.2015.01.026
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compared to expectant management instead of spontaneous labor, metaanalysis of observational studies has revealed a lower chance of cesarean delivery among those who were induced.15 The consequences of labor induction compared to expectant management among women with a prior cesarean remain uncertain. We hypothesized that induction of labor 390/7 weeks of gestation would not be associated with an increased chance of cesarean when compared to expectant management among women planning trial of labor after cesarean. We also investigated whether labor induction is associated with an increase in the risk of uterine rupture or other obstetric morbidities.
M ATERIALS
AND
M ETHODS
This was a secondary analysis of data from the Cesarean Registry of the Eunice
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TABLE 1
Characteristics of women undergoing induction of labor with 1 prior cesarean delivery compared to expectant management IOL
EM
39 e39 wk (n [ 638) 0/7
Characteristic
3/7
IOL
>39 wk (n [ 7565) 3/7
EM
40 e40 wk (n [ 522) 0/7
3/7
IOL
>40 wk (n [ 2933) 3/7
EM
41 e41 wk (n [ 471) 0/7
3/7
>413/7 wk (n [ 547)
Age, y
30.2 5.4b
28.1 5.7
29.7 5.4b
27.7 5.7
28.7 5.5b
27.4 5.6
Prepregnancy BMI
27.0 6.6
26.7 6.3
27.3 6.7
27.0 6.4
27.6 7.3
27.3 6.1
Race African American Caucasian Hispanic Other Cigarette use during
157 (24.6)b 391 (61.3) 55 (8.6)
b
35 (5.5)
b
b
2556 (33.8)
159 (30.4)b
1066 (36.3)
157 (33.3)b
220 (40.2)
2116 (27.9)
b
733 (25.0)
188 (39.9)b
104 (19.0)
973 (33.2)
b
191 (34.9)
2473 (32.7)
75 (11.7)
263 (50.4)
b
69 (13.2) b
421 (5.6)
30 (5.7)
971 (12.8)
69 (13.2)
3228 (42.9)
238 (46.1)
94 (20.0) b
160 (5.4)
32 (6.8)
32 (5.8)
395 (13.5)
67 (14.2)
1270 (43.6)
188 (39.9)b
255 (47.0)
777 (26.5)
117 (24.8)
153 (28.0)
96 (17.6)
Pregnancy Prior vaginal delivery
362 (56.8)b
Prior VBAC
254 (39.8)
b
b
2010 (26.5)
169 (32.4)
Recurrent indication for prior
173 (27.1)b
2475 (39.8)
169 (32.4)
937 (38.5)
145 (30.8)
193 (40.2)
9 (1.4)
63 (0.8)
6 (1.1)
17 (0.6)
4 (0.8)
5 (0.9)
CD Chronic medical illnessa All data presented as mean SD or N (%). BMI, body mass index; CD, cesarean delivery; EM, expectant management; IOL, induction of labor; VBAC, vaginal birth after cesarean. a
Includes chronic hypertension, pregestational diabetes, asthma, seizure disorder, thyroid disease, or renal insufficiency; b P < .05 for comparison of labor induction vs EM at given gestational age.
Palatnik. Induction of labor after prior cesarean delivery. Am J Obstet Gynecol 2015.
Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. That registry was the result of a 4eyear multicenter observational study, designed to address clinical issues related to cesarean childbirth.8 In the present analysis, we included all women from the registry who had a history of 1 cesarean delivery via a low transverse or unknown uterine incision and were at a gestational age of at least 390/7 weeks. Women with scheduled repeat cesarean deliveries done for the indication of prior cesarean delivery were excluded from the analysis. Women who underwent labor induction were divided into 3 comparison groups based on the timing of their induction of labor: 390/7-393/7, 400/7-403/7, and 410/7-413/7 weeks. Gestational age was based on the best obstetric estimate (last menstrual period compared with ultrasonography), determined by health care providers and used for clinical
decision-making.8 Women who underwent induction during each gestational age window were compared with women who were managed expectantly after the same gestational age window. This design was used to mimic the prospective choice of undertaking a labor induction during a given period of time at the start of a given week of gestation or undergoing expectant management from that time forward. In an effort to evaluate women who were not in need of immediate delivery due to the onset of an acute obstetric complication, women were excluded from the induction group when they had an acute obstetric medical indication for induction (ie, preeclampsia, gestational hypertension, nonreassuring antenatal surveillance, oligohydramnios, fetal growth restriction, and antenatal intrauterine fetal demise). However, if women developed these conditions while they were being expectantly managed, they were not
excluded from the expectant management group, as 1 consequence of expectant management is that these conditions may develop and require delivery. A recurrent indication for cesarean delivery was defined as a cesarean due to any type of arrest disorder. Uterine rupture was defined as a disruption or tear of the uterine muscle and visceral peritoneum or a separation of the uterine muscle with extension to the bladder or broad ligament. To ensure that our results were not solely dependent upon our primary analytic approach and group composition, we performed additional analyses in which the inclusion criteria for the group of women expectantly managed was altered slightly. In 1 analysis, we included women who underwent labor from the first day at which women also may have undergone labor induction (ie, laboring women were included in the
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expectantly managed group from 390/7 weeks, instead of only from 394/7 weeks as in the primary analysis). In another analysis, we included women in the expectant management group if they remained pregnant at least 1 week longer than the first day women underwent labor induction in the comparison group but then underwent a scheduled repeat cesarean with prior cesarean as the primary indication, given it is possible that these women initially may have chosen expectant management (instead of planned cesarean) but then decided to forego trial of labor after cesarean when they had not labored by a given gestational age. All analyses were performed with software (Stata, version 12.0; StataCorp, College Station, TX). Univariable comparisons of maternal and neonatal characteristics and pregnancy outcomes were performed using Pearson c2 test and Fisher exact test for categorical data and the Student t test for continuous measures. Additionally, multivariable logistic regression was performed for the outcomes that were significantly different in univariable analysis. Potential confounding variables were entered
into the regression equation if they differed between groups in univariable analysis at a level of P < .05. Odds ratios with 95% confidence intervals were estimated from the logistic regression. This study was considered exempt by the Northwestern University Institutional Review Board because only de-identified data were used.
not reach statistical significance. Women induced at 390/7-393/7 weeks also had a higher chance of uterine rupture compared to women managed expectantly beyond that gestational age (Table 2). There were no other differences in obstetric morbidity between women who were induced and who were expectantly managed. Neonatal characteristics and outcomes are depicted in Table 3. Neonates of women who were induced at 390/7393/7 and 400/7-403/7 weeks had lower birthweight compared to neonates whose mothers were managed expectantly (P < .001 and P ¼ .03, respectively). Overall, neonatal outcomes at each gestational age did not differ significantly among the comparison groups. The point estimates of the frequencies of neonatal intensive care unit admission, hypoxic-ischemic encephalopathy, and perinatal death were higher among neonates whose mothers were in the expectant management groups, however these differences did not reach statistical significance (Table 3). Multivariable analyses for the likelihood of VBAC and uterine rupture are presented in Table 4. Induction of labor
R ESULTS In all, 12,676 women were eligible for analysis. Maternal characteristics of the study population according to the gestational age at which they underwent labor induction or expectant management are depicted in Table 1. Women undergoing induction of labor differed in several ways from those who were expectantly managed, including in their age, race, and obstetric history. Maternal outcomes are depicted in Table 2. Women induced at 390/7-393/7 weeks compared to those who were managed expectantly had higher rates of VBAC. A higher chance of VBAC similarly was noted among women who were induced at 400/7-403/7 weeks, compared to those expectantly managed beyond that gestational age, but the results did
TABLE 2
Outcomes of women undergoing induction of labor after 1 prior cesarean delivery compared to expectant management IOL
EM
IOL
EM
IOL
EM
Maternal outcome
39 e39 wk (n [ 638)
>39 wk (n [ 7565 )
40 e40 wk (n [ 522)
>40 wk (n [ 2933)
41 e41 wk (n [ 471)
>413/7 wk (n [ 547)
VBAC
471 (73.8)b
4640 (61.3)
340 (65.1)
1817 (61.9)
277 (58.8)
330 (60.3)
Third/fourth degree
28 (4.4)
311 (4.1)
30 (5.7)
108 (3.7)
27 (5.7)
14 (2.5)
Endometritis
13 (2.0)
255 (3.4)
12 (2.3)
115 (3.9)
20 (4.2)
16 (2.9)
4 (0.6)
29 (0.4)
4 (0.7)
12 (0.4)
1 (0.2)
2 (0.3)
6 (0.9)
122 (1.6)
14 (2.7)
45 (1.5)
9 (1.9)
11 (2.0)
22 (0.3)
4 (0.7)
10 (0.3)
0
0/7
Wound complication Blood transfusion Operative complications
a
3/7
1 (0.1) b
3/7
0/7
3/7
3/7
0/7
3/7
1 (0.2)
Uterine rupture
9 (1.4)
40 (0.5)
7 (1.3)
17 (0.6)
6 (1.3)
2 (0.4)
Hysterectomy
0
11 (0.1)
3 (0.6)
5 (0.2)
0
3 (0.5)
ICU admission
1 (0.1)
21 (0.3)
3 (0.6)
7 (0.2)
0
1 (0.2)
Maternal death
0
1 (0.2)
0
0
0
1 (0.01)
All data presented as mean SD or N (%). EM, expectant management; ICU, intensive care unit; IOL, induction of labor; VBAC, vaginal birth after cesarean. a
Cystotomy, ureteral injury, bowel injury; b P < .05 for comparison of labor induction vs EM at given gestational age.
Palatnik. Induction of labor after prior cesarean delivery. Am J Obstet Gynecol 2015.
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TABLE 3
Neonatal outcomes of women undergoing induction of labor after 1 prior cesarean delivery compared to expectant management IOL
EM
39 e39 wk (n [ 638) 0/7
Variable Male
3/7
309 (48.4)
Birthweight, g
3416 448
b
5-min Apgar score 5 Umbilical artery pH 7.0 Admission to NICU
2 (0.3)
IOL
>39 wk (n [ 7565 ) 3/7
46 (7.2)
40 e40 wk (n [ 522) 3/7
3805 (50.3)
271 (51.9)
3527 461
3543 443
60 (0.8)
5/183 (2.7)
EM
0/7
b
>40 wk (n [ 2933)
703 (9.3)
5/169 (2.9) 48 (9.2)
EM
41 e41 wk (n [ 471) 0/7
3/7
>413/7 wk (n [ 547)
1517 (51.7)
241 (51.2)
285 (52.1)
3591 466
3645 428
3600 493
4 (0.8)
58/3445 (1.7)
IOL 3/7
24 (0.8) 30/1417 (2.1)
2 (0.4)
8 (1.4)
3/172 (1.7)
6/294 (2.0)
39 (8.3)
64 (11.7)
309 (10.5)
Antepartum or intrapartum death
0
9 (0.1)
0
4 (0.1)
0
4 (0.7)
Hypoxic-ischemic Encephalopathy
0
5 (0.06)
1 (0.2)
2 (0.07)
0
1 (0.2)
Neonatal death
0
3 (0.04)
0
1 (0.03)
0
0
Perinatal deatha
0
0
5 (0.2)
0
4 (0.7)
12 (0.1)
All data presented as mean SD or N (%). EM, expectant management; IOL, induction of labor; NICU, neonatal intensive care unit; VBAC, vaginal birth after cesarean. a
Antepartum, intrapartum, or neonatal death; b P < .05 for comparison of labor induction vs EM at given gestational age.
Palatnik. Induction of labor after prior cesarean delivery. Am J Obstet Gynecol 2015.
at 390/7-393/7 weeks continued to be associated with a significantly higher chance of VBAC compared to expectant management. Although induction of labor at later gestational ages also was associated with higher odds of VBAC, this difference did not reach statistical significance. Similarly, in the
multivariable analysis, induction of labor at 390/7-393/7 weeks compared to expectant management was associated with a higher risk of uterine rupture; this association did not reach statistical significance when labor inductions were compared to expectant management at later gestational ages. Results did not
TABLE 4
Association of labor induction with VBAC and uterine rupture compared to expectant management OR
95% CI
aORa
95% CI
390/7e393/7
1.78
1.48e2.13
1.31
1.03e1.67
40 e40
3/7
1.15
0.94e1.39
1.21
0.93e1.56
41 e41
3/7
0.94
0.73e1.21
1.04
0.76e1.43
390/7e393/7
2.69
1.30e5.57
2.73
1.22e6.12
40 e40
3/7
2.33
0.96e5.65
2.31
0.84e6.33
41 e41
3/7
3.52
0.71e17.50
3.13
0.58e16.88
Gestational age at IOL, wk VBAC 0/7 0/7
Risk of uterine rupture 0/7 0/7
aOR, adjusted odds ratio; CI, confidence interval; IOL, induction of labor; OR, odds ratio; VBAC, vaginal birth after cesarean. a
Adjusted for maternal age, race, recurrent indication for prior cesarean delivery, presence of prior vaginal delivery, and presence of prior VBAC.
Palatnik. Induction of labor after prior cesarean delivery. Am J Obstet Gynecol 2015.
differ for the analyses that used different inclusion criteria to construct the expectant management group.
C OMMENT In this secondary analysis we sought to evaluate outcomes in women who were at least 390/7 weeks of gestation with 1 prior cesarean delivery and who underwent induction of labor vs expectant management. We found that the rates of both VBAC and uterine rupture were higher among women undergoing induction of labor at 390/7-393/7 weeks compared to those undergoing expectant management. A similar pattern in these outcomes was seen with induction of labor at later gestational ages, although the differences did not reach statistical significance, perhaps because of lesser power associated with a smaller sample size. Other maternal and neonatal outcomes were similar between the 2 groups. The results of this study in regard to VBAC are in contrast to the results of those studies that have compared labor induction with spontaneous labor. These cohort studies of nulliparous women described approximately a 2-fold increased risk of cesarean delivery with
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induction of labor.6,7,16-18 However, as has been noted by others, to evaluate outcomes associated with labor induction in an actual clinical context, the relevant clinical comparison is between labor induction and expectant management.12-14 When this comparison has been made among women without a prior cesarean, induction of labor 39 weeks actually has been associated with a lower chance of cesarean.14,19-22 One group of investigators who evaluated women with a prior cesarean also found that labor induction was associated with a lower chance of cesarean.23 This study additionally suggested that there was no difference in the risk of uterine rupture associated with labor induction or perinatal mortality, although there was a significant increase in the frequency of neonatal intensive care unit admission and postpartum hemorrhage among women who underwent labor induction at some gestational ages. However, the data source used was an administrative database collected over >3 decades; such a data source may be prone to multiple biases.24 In contrast, our study used a database derived from direct chart abstraction by trained research nurses. Nevertheless, our results that labor induction was associated with a lower chance of repeat cesarean and a greater chance of VBAC are similar to those of Stock et al.23 In contrast, our result with regard to the association between labor induction and uterine rupture is not consistent with that of Stock et al,23 but is consistent with other observational studies, even if those studies used spontaneous labor as the comparison group.3,9-10 A recent metaanalysis comparing induction and spontaneous labor after prior cesarean showed 1.6-fold increase in the incidence of uterine rupture with induction (95% confidence interval, 1.13e2.31).25 Similarly, in this study, the odds of uterine rupture in the context of labor induction were approximately doubled, although the attributable risk increase was <1%. The limitations of this analysis should be noted. First, we did not know the cervical examination at the time expectant management was pursued and thus
could not account for cervical status in stratified or regression analysis. This inability could potentially bias our results if, for example, women who were managed expectantly were more likely to have unfavorable cervices compared to those who were induced. Another limitation is the fixed sample size of the overall cohort. Although our comparison of maternal and neonatal outcomes did not reach statistical significance among women at 400/7 weeks of gestation, it is possible that this is due to the relatively smaller size of these subgroups and a corresponding reduction in the power to detect a difference. There also could be other unmeasured differences between the groups that could explain the observed associations. Lastly, because of its observational nature we cannot know that a prospective policy of labor induction, either electively or for particular medical indications, would result in the same outcomes. Labor induction for women with a prior cesarean delivery is considered acceptable practice by the American Congress of Obstetricians and Gynecologists.1 Nevertheless, the final determination of whether a labor induction should be undertaken needs to be made by a woman, informed of the risks and benefits, who is working with her physician to ascertain her most preferred approach to delivery based on her individual circumstances. The results of this study can help provide guidance to women and their providers during this decisionmaking process. ACKNOWLEDGMENT We would like to acknowledge the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the Maternal-Fetal Medicine Units Network, and the Protocol Subcommittee for making this database publically available.
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