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Model for Predicting Vaginal Birth After Cesarean Section (VBAC)

Purpose: To evaluate a pregnant woman with a history of cesarean section for the chance of vaginal delivery using the nomogram of Grobman et al.

Description

Grobman et al developed a nomogram for identifying a woman who is able to have a vaginal birth after a cesarean section (VBAC). The authors are from the Maternal-Fetal Units Network (MFMU) sponsored by the National Institute of Child Health and Human Development (NICHD).


Parameters (can be determined on the first prenatal visit):

(1) age in years

(2) body mass index (BMI)

(3) race

(4) vaginal delivery since last cesarean section

(5) previous vaginal delivery

(6) recurrent primary indication for previous C-section (arrest of cervical dilation or descent)

 

points for age in years =

= 19.57 - (0.391 * (age))

 

points for body mass index =

= 45 - (0.6 * (BMI))

 

Parameter

Finding

Points

African-American

no

7

 

yes

0

Hispanic

no

7

 

yes

0

vaginal delivery since cesarean

no

0

 

yes

10

previous vaginal delivery

no

0

 

yes

9

recurrent primary indication

no

6

 

yes

0

 

where:

• In theory a patient could be both Hispanic and Black, although this usage is not discussed in the paper.

• In theory responses could include No to previous vaginal delivery and Yes to vaginal delivery since C-section.

 

total score =

= SUM(points for all 6 parameters)

 

Score

Probability of Vaginal Delivery After a Trial of Labor

< 17

< 5%

17 to 38

11.87 - (1.109 * (points)) + (0.04144 * ((points)^2))

38 to 55

-65.98 + (2.619 * (points)) - (0.002847 * ((points)^2))

55 to 76

-167.2 + (6.536 * (points)) - (0.04062 * ((points)^2))

> 76

> 95%


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Specialty

Objective

ICD-10