Giving birth can be a complicated experience that may be overwhelming, exhausting and a miracle. The birthing process over the years has changed and more women are delivering via cesarean section. In 2009, 32.9% of births in the United States were accomplished by cesarean section (1). Once a woman has had one cesarean section the options for the next delivery are to have a repeat cesarean section or attempt a trial of labor that could result in a vaginal birth after cesarean (VBAC). There are risks and benefits associated with both options, but each should be presented to the patient in an educated manner.
Many factors go into choosing a method of delivery that is safe for the mother and baby. VBAC is successful approximately 70% of the time (2), but this is a very vague statistic. The chance of a successful VBAC depends on many factors that should be addressed early in the pregnancy and as labor progresses. The following studies address certain criteria that need to be considered when calculating individual probability of success for a VBAC. This information is to be used to inform both provider and mother of the best educated prediction on the unpredictable event of birth.
Flamm Admission Scoring
An admission scoring system was introduced by Flamm and colleagues (1997), through a prospective cohort study of women who had a previous cesarean section. The researchers calculated a predictive score of having a successful VBAC based on the data gathered from the females at admission to the hospital through a multivariate logistic regression model. This model allowed for five significant variables (Table 1) to be identified at time of labor that can be calculated into a point system to determine the probability of attempting a successful VBAC. The higher the point score the more likely a successful VBAC with 10 being the highest and 0 being the lowest. According to Flamm’s criteria, the rate of success for a VBAC ranged from 49% based on scores ranging 0-2 and 95% with scores of 8-10. Two-thirds of the patients in the score testing group with 4 or more points delivered vaginally (3). A limitation to the study was the criteria can only be utilized at the onset of labor and an informed decision to precede with a VBAC needs to be discussed beforehand.
Flamm’s criteria allowed new insight on VBAC for almost half the women in his study, which allowed for a better predictive score than the general 60-80% success rate (flamm and EDEN). His research was validated internally(Flamm) and externally (dinsmoor) with performances similar to the original reported findings. However, even after being validated, this criteria is not used frequently in hospitals or by physicians (guise).
Gonen Score (4)
A different approach to predicting the probability of a successful VBAC was created by Gonen and colleagues (2004) by looking at variables based on three stages: first prenatal visit, onset of labor, and during labor. The researchers calculated which...