Point-of-Care Guides

Predicting the Likelihood of Successful Vaginal Birth After Cesarean Delivery

Am Fam Physician. 2007 Oct 15;76(8):1192-1194.

Clinical Question

Which patients are likely to have a successful vaginal birth after a previous cesarean delivery?

Evidence Summary

The American College of Obstetricians and Gynecologists and the American Academy of Family Physicians recommend that pregnant women with a single previous cesarean delivery and a low-transverse incision be offered a trial of labor.1,2 Although the rate of vaginal birth after cesarean delivery (VBAC) increased from 19 percent of all deliveries in 1989 to a peak of 28 percent in 1996, the rate decreased to only 9.2 percent of all deliveries in 2004.3,4 The decline has been partially driven by concerns about the small but measurable risk of uterine rupture with VBAC, particularly when labor is induced or augmented.5

At the same time, the total number of cesarean deliveries has been increasing, largely because of an increase in primary cesarean deliveries.3 A screening tool to help predict whether a woman will have a successful VBAC may help patients and their physicians make more informed shared decisions.

A 2003 evidence review by the Agency for Healthcare Research and Quality found overall VBAC success rates between 60 and 82 percent in published studies, with an estimated overall success rate of 75 percent at teaching institutions and tertiary medical centers. The risks of perinatal death or hysterectomy from uterine scar rupture were low (1.5 and 4.8 per 10,000 births, respectively).4 The review identified factors associated with an increased likelihood of vaginal delivery (i.e., maternal age younger than 40 years, previous successful vaginal delivery, and favorable cervical factors). The review also identified factors that decreased the likelihood of vaginal birth (i.e., more than one previous cesarean delivery; induction of labor; birth weight greater than 4,000 g [8 lb, 13 oz]; and gestational age greater than 40 weeks).4

A number of researchers have attempted to develop clinical decision rules to predict the likelihood of a successful trial of labor after a previous cesarean delivery. A 2004 systematic review identified six of these clinical decision rules,6 two of which were validated (i.e., tested in a new population to confirm accuracy of the rule).7,8 Three subsequent rules were developed and validated.911  These five validated rules are summarized in Table 1.711

Table 1

Summary of Clinical Decision Rules to Predict Successful VBAC

Study Population characteristics Number of patients Variables Type of rule
Development group Validation group

Troyer, et al., 19928

Previous low-transverse cesarean delivery, gestational age > 36 weeks

264

236

No previous vaginal birth, nonreassuring fetal heart tone at admission, induction of labor, previous dysfunctional labor

Additive point score

Flamm, et al., 19977

Previous low-transverse cesarean delivery, gestational age ≥ 37 weeks

2,502

2,501

Maternal age, history of vaginal birth, a reason other than failure to progress for first cesarean delivery, cervical effacement at admission, cervical dilation ≥ 4 cm at admission

Additive point score

Smith, et al., 200510

Single previous low-transverse cesarean delivery, gestational age ≥ 40 weeks

11,643

11,643

Maternal height, maternal age, previous vaginal birth, gestational age, method of induction, sex of infant

Multiplicative score

Grobman, et al., 200711

Single previous low-transverse cesarean delivery, gestational age ≥ 37 weeks

5,928

5,928

Maternal age, body mass index, race, vaginal birth since last cesarean delivery, previous vaginal birth, nonrecurrent indication*

Logistic regression equation and nomogram

Hashima, et al., 20079

Single previous low-transverse cesarean delivery

5,414

5,414

Recurrent indication,* no history of fetal macrosomia, no current maternal anemia

Additive point score


VBAC = vaginal birth after cesarean delivery.

*— Reccurent indication is a reason other than cephalopelvic disproportion, failure to progress, or arrest of labor for first cesarean delivery.

Information from references 7 through 11.

Table 1   Summary of Clinical Decision Rules to Predict Successful VBAC

View Table

Table 1

Summary of Clinical Decision Rules to Predict Successful VBAC

Study Population characteristics Number of patients Variables Type of rule
Development group Validation group

Troyer, et al., 19928

Previous low-transverse cesarean delivery, gestational age > 36 weeks

264

236

No previous vaginal birth, nonreassuring fetal heart tone at admission, induction of labor, previous dysfunctional labor

Additive point score

Flamm, et al., 19977

Previous low-transverse cesarean delivery, gestational age ≥ 37 weeks

2,502

2,501

Maternal age, history of vaginal birth, a reason other than failure to progress for first cesarean delivery, cervical effacement at admission, cervical dilation ≥ 4 cm at admission

Additive point score

Smith, et al., 200510

Single previous low-transverse cesarean delivery, gestational age ≥ 40 weeks

11,643

11,643

Maternal height, maternal age, previous vaginal birth, gestational age, method of induction, sex of infant

Multiplicative score

Grobman, et al., 200711

Single previous low-transverse cesarean delivery, gestational age ≥ 37 weeks

5,928

5,928

Maternal age, body mass index, race, vaginal birth since last cesarean delivery, previous vaginal birth, nonrecurrent indication*

Logistic regression equation and nomogram

Hashima, et al., 20079

Single previous low-transverse cesarean delivery

5,414

5,414

Recurrent indication,* no history of fetal macrosomia, no current maternal anemia

Additive point score


VBAC = vaginal birth after cesarean delivery.

*— Reccurent indication is a reason other than cephalopelvic disproportion, failure to progress, or arrest of labor for first cesarean delivery.

Information from references 7 through 11.

Although the Troyer rule was validated, the number of patients in the validation group was small.8 The Hashima rule was also prospectively validated; however, only three out of 5,414 women had a score of 0, and only 101 had a score of 1 (low probability of success).9 The remaining 5,310 women had scores of 2 (53 percent success rate) or 3 (67 percent success rate), which provides little useful information for decision making.9

The remaining three scores were well validated and were shown to be accurate in a large, representative population.7,10,11  The Flamm rule (Table 2) is the simplest to use, although it is limited by its age (data were gathered between 1990 and 1992) and by the requirement of cervical effacement information, which makes it unhelpful for antepartum planning.7

Table 2

Flamm Clinical Decision Rule for Predicting Successful VBAC

Patient characteristics Points

Maternal age < 40 years

2

Vaginal birth history (choose one)

Vaginal birth before and after first cesarean delivery

4

Vaginal birth after first cesarean delivery

2

Vaginal birth before first cesarean delivery

1

No previous vaginal birth

0

Reason other than failure to progress for first cesarean delivery

1

Cervical effacement at admission

> 75 percent

2

25 to 75 percent

1

< 25 percent

0

Cervical dilation ≥ 4 cm at admission

1

Total:

____

Score Number of women with this score Percentage of women with successful VBAC

0 to 2

114

49

3

329

60

4

595

67

5

660

77

6

360

88

7

189

93

8 to 10

158

95


VBAC = vaginal birth after cesarean delivery.

Adapted with permission from Flamm BL, Geiger AM. Vaginal birth after cesarean delivery: an admission scoring system. Obstet Gynecol 1997;90:909. (http://lww.com)

Table 2   Flamm Clinical Decision Rule for Predicting Successful VBAC

View Table

Table 2

Flamm Clinical Decision Rule for Predicting Successful VBAC

Patient characteristics Points

Maternal age < 40 years

2

Vaginal birth history (choose one)

Vaginal birth before and after first cesarean delivery

4

Vaginal birth after first cesarean delivery

2

Vaginal birth before first cesarean delivery

1

No previous vaginal birth

0

Reason other than failure to progress for first cesarean delivery

1

Cervical effacement at admission

> 75 percent

2

25 to 75 percent

1

< 25 percent

0

Cervical dilation ≥ 4 cm at admission

1

Total:

____

Score Number of women with this score Percentage of women with successful VBAC

0 to 2

114

49

3

329

60

4

595

67

5

660

77

6

360

88

7

189

93

8 to 10

158

95


VBAC = vaginal birth after cesarean delivery.

Adapted with permission from Flamm BL, Geiger AM. Vaginal birth after cesarean delivery: an admission scoring system. Obstet Gynecol 1997;90:909. (http://lww.com)

The Smith rule is well validated but is based on a multivariate equation, making it too complex for practical use at the point of care.10 Although the Grobman rule is also based on a complex multivariate equation, a nomogram (Figure 1) is provided for use at the point of care.11 The Grobman rule has been well validated and all of the needed variables are available to the patient and physician before the onset of labor.

Predicting the Successful VBAC

Figure 1.

Nomogram for predicting successful vaginal birth after cesarean delivery (VBAC). Assign a point value for each risk factor by drawing a line from the risk factor to the point scale at the top of the nomogram, then add up the total points. Find the likelihood of successful VBAC by drawing a line from the total points to the probability (%) scale at the bottom of the nomogram.

Reprinted with permission from Grobman WA, Lai Y, Landon MB, Spong CY, Leveno KJ, Rouse DJ, et al., for the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. Development of a nomogram for prediction of vaginal birth after cesarean delivery. Obstet Gynecol 2007;109:810. (http://lww.com)

View Large

Predicting the Successful VBAC


Figure 1.

Nomogram for predicting successful vaginal birth after cesarean delivery (VBAC). Assign a point value for each risk factor by drawing a line from the risk factor to the point scale at the top of the nomogram, then add up the total points. Find the likelihood of successful VBAC by drawing a line from the total points to the probability (%) scale at the bottom of the nomogram.

Reprinted with permission from Grobman WA, Lai Y, Landon MB, Spong CY, Leveno KJ, Rouse DJ, et al., for the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. Development of a nomogram for prediction of vaginal birth after cesarean delivery. Obstet Gynecol 2007;109:810. (http://lww.com)

Predicting the Successful VBAC


Figure 1.

Nomogram for predicting successful vaginal birth after cesarean delivery (VBAC). Assign a point value for each risk factor by drawing a line from the risk factor to the point scale at the top of the nomogram, then add up the total points. Find the likelihood of successful VBAC by drawing a line from the total points to the probability (%) scale at the bottom of the nomogram.

Reprinted with permission from Grobman WA, Lai Y, Landon MB, Spong CY, Leveno KJ, Rouse DJ, et al., for the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. Development of a nomogram for prediction of vaginal birth after cesarean delivery. Obstet Gynecol 2007;109:810. (http://lww.com)

Applying the Evidence

A 25-year-old, non-Hispanic, white woman with a body mass index (BMI) of 25 kg per m2 is in labor. Her cervix is 3 cm dilated and about 30 to 40 percent effaced. She has had one previous pregnancy, which resulted in cesarean delivery because of failure to progress. She wonders how likely it is that a trial of labor will be successful.

Answer: Using the Flamm rule (Table 27), the patient receives two points for age and one for cervical effacement. The total score of 3 gives her a 60 percent probability of vaginal delivery. Using the Grobman nomogram (Figure 111), the patient receives 10 points for age, 30 for body mass index, 7 points each for being non–African American and non-Hispanic, and 0 for no history of vaginal birth or recurrent primary indication. The total score of 54 points gives her a 68 percent probability of vaginal delivery. You advise the patient that her chance of a successful trial of labor is about two out of three.

Address correspondence to Mark H. Ebell, MD, MS, at mebell@mcg.edu. Reprints are not available from the author.

REFERENCES

1. American College of Obstetricians and Gynecologists. Vaginal birth after previous cesarean. ACOG Practice Bulletin No. 54. Obstet Gynecol. 2004;104:203–12.

2. American Academy of Family Physicians. AAFP policy on trial of labor after cesarean (TOLAC). Accessed August 19, 2007, at: http://www.aafp.org/about/policies/all/cesarean-delivery.html.

3. Martin JA, Hamilton BE, Sutton PD, Ventura SJ, Menacker F, Kirmeyer S. Births: final data for 2004. Hyattsville, Md.: National Center for Health Statistics, 2006. DHHS publication no. (PHS) 2006-1120. Accessed July 10, 2007, at: http://www.cdc.gov/nchs/data/nvsr/nvsr55/nvsr55_01.pdf.

4. Guise J-M, McDonagh MS, Hashima J, Kraemer DF, Eden KB, Berlin M, et al. Vaginal birth after cesarean (VBAC) volume 1 and volume 2. Rockville, Md.: Agency for Healthcare Research and Quality, March 2003. AHRQ publication no. 03-E018. Accessed July 10, 2007, at: http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=hstat1a.chapter.7149.

5. Landon MB, Hauth JC, Leveno KJ, Spong CY, Leindecker S, Varner MW, et al. , for the 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.

6. Hashima JN, Eden KB, Osterweil P, Nygren P, Guise JM. Predicting vaginal birth after cesarean delivery: a review of prognostic factors and screening tools. Am J Obstet Gynecol. 2004;190:547–55.

7. Flamm BL, Geiger AM. Vaginal birth after cesarean delivery: an admission scoring system. Obstet Gynecol. 1997;90:907–10.

8. Troyer LR, Parisi VM. Obstetric parameters affecting success in a trial of labor: designation of a scoring system. Am J Obstet Gynecol. 1992;167(4 pt 1):1099–104.

9. Hashima JN, Guise JM. Vaginal birth after cesarean: a prenatal scoring tool. Am J Obstet Gynecol. 2007;196:e22–3.

10. Smith GC, White IR, Pell JP, Dobbie R. Predicting cesarean section and uterine rupture among women attempting vaginal birth after prior cesarean section. PLoS Med. 2005;2:e252.

11. Grobman WA, Lai Y, Landon MB, Spong CY, Leveno KJ, Rouse DJ, et al. , for the National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network Development of a nomogram for prediction of vaginal birth after cesarean delivery. Obstet Gynecol. 2007;109:806–12.

This guide is one in a series that offers evidence-based tools to assist family physicians in improving their decision making at the point of care.


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