VBAC and Induction or Acceleration of Labour

A number of studies have found that induction or acceleration of labour in mothers attempting a vaginal birth after caesarean (VBAC) carries an increased risk of uterine rupture. Others have found no such link. Some of the more recent studies are summarised here. I will not summarise the older studies as these are thoroughly discussed on other sites, eg the Midwife Archives page on Pitocin and VBAC

If induction of labour in VBAC mothers does carry an increased risk of uterine rupture, this does not imply that such mothers should never be induced, or have their labours accelerated. If the alternative is an elective repeat caesarean then induction of labour may still be the best course overall. However, it does suggest that induction and acceleration of labour should be undertaken only with care, and avoided when possible.

The studies on this page consider induction with oxytocin (pitocin, syntocinon), usually given as a 'drip', or intravenous infusion, and induction generally, using oxytocin or prostaglandins. Another common method of inducing labour and ripening the cervix is using Prostaglandin E2 Gel (Prostin), or more rarely, misoprostol (Cytotec). These drugs are considered on separate pages.

Prostaglandin E2 Gel and VBAC

Misoprostol (Cytotec) and VBAC

For more discussion, see the Midwife Archives page on Pitocin and VBAC.

Laura Brockman's baby, Stephen, died after her uterus ruptured following induction of labour. She has asked for her story to be told to help other women avoid such tragedy.

The study below reassured obstetricians that no link was found between induction of labour and uterine rupture in VBAC candidates. However, it was a meta-analysis published in 1991 and the component studies must therefore be older. There are a number of more recent studies which raise new questions about the safety of induction of labour in mothers attempting VBAC.

Vaginal birth after cesarean: a meta-analysis of morbidity and mortality.

Obstet Gynecol 1991 Mar;77(3):465-70
Rosen MG, Dickinson JC, Westhoff CL
Department of Obstetrics and Gynecology, Sloane Hospital for Women, Presbyterian Hospital, New York, New York.

The authors looked at 31 studies giving a total of 11,417 attempts at VBAC. They found that:

After excluding babies dead before labour started, those with deformities incompatible with life, and babies of extremely low birthweight, there was no difference in perinatal death rates between babies born after VBAC attempts and those born after elective repeat caesareans.

More babies had low 5-minute Apgar scores (6 or lower) after VBAC attempts, but the researchers were unable to exclude very low birth weight fetuses or those with congenital anomalies from this analysis.

The authors conclude: "Our findings argue for trials of labor for more women after a cesarean birth."

Read the abstract on Medline

This study, published in 1987, also gave reassuring results:

Oxytocin during labor after previous cesarean section: results of a multicenter study

Obstetrics & Gynecology. 70(5):709-12, 1987 Nov
Flamm BL. Goings JR. Fuelberth NJ. Fischermann E. Jones C. Hersh E.
Department of Obstetrics and Gynecology, Kaiser Permanente Medical Centers, California.

"This paper presents a series of 1776 patients allowed to labor after a previous cesarean section, of whom 485 (27%) were treated with oxytocin. When the patients who received oxytocin were compared with those who did not, no significant differences were found with respect to uterine rupture, maternal morbidity, fetal morbidity, or fetal mortality. We conclude that the judicious use of oxytocin is safe in the patient with a previous low transverse cesarean section."

The following is the most recent VBAC rupture study which I have found. The researchers analysed cases of uterine ruptures and compared them to women who had a VBAC without rupture. They concluded that the use of oxytocin and prostaglandin gel were risk factors, along with instrumental delivery, and that they were particularly risky for a woman who was having her first VBAC attempt.

Successful first vaginal birth after cesarean section: a predictor of reduced risk for uterine rupture in subsequent deliveries.

Isr Med Assoc J 2000 Jul;2(7):526-8
Shimonovitz S, Botosneano A, Hochner-Celnikier D
Department of Obstetrics and Gynecology, Hadassah University Hospital, Mt. Scopus, Jerusalem, Israel.

BACKGROUND: Uterine rupture is a catastrophic obstetric complication, most often associated with a preexisting cesarean section scar. Although a vaginal birth after a cesarean is considered safe in modern obstetrics, it is not known whether repeated VBACs increase the risk of rupture, or whether the first VBAC proves the strength and durability of the scar, predicting further successful and less risky vaginal deliveries.

OBJECTIVES: To evaluate the effect of repeated vaginal deliveries on the risk of uterine rupture in women who have previously delivered by cesarean section.

METHODS: In this retrospective study, 26 VBAC deliveries complicated by uterine rupture were matched for age, parity, and gravidity with 66 controls who achieved VBAC without rupture. The histories, demography, pregnancy, labor and delivery records, as well as neonatal outcome were compared.

RESULTS: We found that the risk of rupture decreases dramatically in subsequent VBACs. Of the 40 cases of uterine rupture recorded during the 18 year study period, 26 occurred during VBAC deliveries. Of these, 21 were complicated first VBACs. We also found that the use of prostaglandin-estradiol, instrumental deliveries, and oxytocin had been used significantly more often during deliveries complicated with rupture than in VBAC controls.

CONCLUSIONS: Once a woman has achieved VBAC the risk of rupture falls dramatically. The use of oxytocin, PGE2 and instrumental deliveries are additional risk factors for rupture, therefore caution should be exerted regarding their application in the presence of a uterine scar, particularly in the first vaginal birth after cesarean.

PMID: 10979328, UI: 20433706

Medline Abstract

The next paper, published in 1999, is among the most recent of the VBAC studies and we can assume that the researchers will have been familiar with previous research on the matter. Its findings are worrying.

Uterine rupture during induced or augmented labor in gravid women with one prior cesarean delivery.

Am J Obstet Gynecol 1999 Oct;181(4):882-6
Zelop CM, Shipp TD, Repke JT, Cohen A, Caughey AB, Lieberman E
Department of Obstetrics and Gynecology, Massachusetts General Hospital, the Department of Obstetrics and Gynecology, Brigham and Women's Hospital, Harvard Medical School, and the Department of Obtetrics and Gynecology, University of Nebras.

The study looked at 2774 women attempting VBAC at term, after 1 prior cesarean delivery and no other births. It compared the rates of uterine rupture associated with spontaneous labour, oxytocin induction or acceleration, and prostaglandin E2 gel induction. The analysis controlled for other factors which might confuse the result, such as birth weight, use of epidural, duration of labour, maternal age, year of delivery, and years since last birth.

Of 2774 women in the analysis, 2214 had spontaneous onset of labor and 560 women had labor induced with oxytocin or prostaglandin E(2) gel. 1072 women had their labours accelerated ('augmented') with oxytocin.

The overall rate of rupture among all patients with induction of labor was 2.3%, in comparison with 0.7% among women with spontaneous labor. Among 1072 patients receiving oxytocin augmentation, the rate of uterine rupture was 1.0%, in comparison with 0.4% in nonaugmented, spontaneously laboring patients.

After adjusting for birth weight, use of epidural, duration of labor, maternal age, year of delivery, and years since last birth, induction with oxytocin was associated with a 4.6-fold increased risk of uterine rupture compared with no oxytocin use. Acceleration with oxytocin made uterine rupture was 2.3 times more likely, and use of prostaglandin E(2) gel made rupture 3.2 times more likely. These differences did not qualify as statistically significant though, because of the small numbers involved.

CONCLUSION: "Induction of labor with oxytocin is associated with an increased rate of uterine rupture in gravid women with 1 prior uterine scar in comparison with the rate in spontaneously laboring women. Although the rate of uterine rupture was not statistically increased during oxytocin augmentation, use of oxytocin in such cases should proceed with caution."

This is the most recent of the VBAC induction studies:

Uterine Rupture During Induced Trials Of Labour In Women With A Previous Cesarean Delivery

American Journal of Obstetrics and Gynecology, January 2000, in two parts, part 2, volume 182, number one

D. Ravasiax S. Woodx J. Pollard
University of Calgary, Foothills Hospital, Calgary, AB, Canada

OBJECTIVE: To determine the rate of uterine rupture during induced trials of labour (TOL) after previous cesarean delivery compared to spontaneous TOL.

STUDY DESIGN: Rates of uterine rupture were determined for all inductions in women with a prior cesarean section and for each mode of induction, including prostaglandin E2 gel (PGE2), intracervical Foley catheter (This is like a mechanical version of a slow stretch and sweep of the membranes), artificial rupture of membranes (ARM) and oxytocin. Comparisons were made with Fishers's exact test.

RESULTS: Between 1992 and 1998, there were 2119 TOL, 575 of which were induced (27%). The overall rate of uterine rupture was 15/2119 (0.71%). The uterine rupture rate with induced TOL (8/575, 1.4%) was significantly higher than with spontaneous TOL (7/1544, 0.45%), p=0.036. The relative risk of uterine rupture with induction was 3.09 (95% CI 1.12 to 8.42). Uterine rupture rates by method of induction (alone or in combination with another) are shown in the table below and are compared with uterine rupture during spontaneous TOL.

Induction Method Number of Ruptures Number of women Rupture rate p-value
PGE2 5 172 2.9% 0.004
ARM 2 130 1.5% 0.15
Foley 1 130 0.76% 0.47
Oxytocin 5 427 1.2% 0.15
Spontaneous TOL 7 1544 0.45%

The relative risk of uterine rupture with PGE2 use versus spontaneous TOL was 6.41 (95% CI 2.06 - 19.98). The relative risk for Foley catheter induction compared with spontaneous TOL was 1.70 (95% CI 0.21 to 13.69).


  1. The rate of uterine rupture with induced trial of labour (TOL) is significantly higher than with spontaneous trial of labour.
  2. PGE2 exposure during TOL is associated with more than a 6-fold increase in uterine rupture when compared to spontaneous TOL.
  3. Foley catheter induction is associated with the lowest rupture rate in the induced TOL group and is comparable to spontaneous TOL.

Latent labor with an unknown uterine scar

Grubb DK, Kjos SL, Paul
Obstet Gynecol 1996 Sep;88(3):351-5
Department of Obstetrics and Gynecology, University of Southern California, Los Angeles, USA.

OBJECTIVE: To determine if avoiding the augmentation of ineffective contractions in women with unknown uterine scars would decrease the risk of cesarean for protraction disorders, compared with awaiting the onset of spontaneous labor


METHODS: Term gravidas with one or two unknown uterine scars in early labor were randomized to nonintervention (N = 101) and intervention (N = 96) groups. Nonintervention subjects were discharged if cervical change did not occur within 4 hours. Intervention subjects were admitted. Contractions that persisted for 4 hours without cervical change were augmented with oxytocin.

RESULTS: Intervention subjects received oxytocin significantly more often (82 versus 55%, P < .001) and had a statistically significantly higher rate of uterine scar separation (5 versus 0%, P = .03). There was no difference between the two groups in length of active labor (4.0 versus 4.25 hours) or incidence of cesarean delivery (16 versus 17%).

CONCLUSION: The augmentation of ineffective contractions during latent labor in gravidas with an unknown uterine scar does not increase the rate of cesarean delivery, but it is significantly more likely to result in uterine scar separations.


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