Use of calculators and models for predicting vaginal birth after a previous cesarean delivery
- Torri D Metz, MD
Torri D Metz, MD
- Assistant Professor
- Maternal-Fetal Medicine
- University of Colorado Denver
After a first cesarean delivery, a pregnant woman has to choose between an elective repeat cesarean delivery (ERCD) and a trial of labor after cesarean (TOLAC) with the goal of achieving a vaginal birth (VBAC). In order to make this decision, both clinicians and patients typically desire individualized information about (1) the chance of VBAC and (2) the balance between the risks of maternal or fetal morbidity with TOLAC compared with ERCD.
This information is also important on a population level, especially in the setting of a rising cesarean delivery rate, as selection of candidates who are most likely to deliver vaginally after a previous cesarean can minimize the costs of ERCD and failed TOLAC. The cost-effectiveness of TOLAC is dependent on the likelihood of VBAC. In a decision analytic model with a hypothetical cohort of 100,000 women undergoing TOLAC versus ERCD, TOLAC was cost-effective when the likelihood of VBAC was >47.2 percent . In another study, if all women who were calculated to be good candidates for VBAC underwent TOLAC, the cesarean rate would have been reduced from 70.4 to 25.5 percent (assuming a VBAC rate of 70 percent) .
This topic will discuss the use of calculators for counseling women about TOLAC. All other issues related to TOLAC are reviewed separately. (See "Choosing the route of delivery after cesarean birth".)
The goal of TOLAC calculators and models is to predict a woman's chance of VBAC based on her demographic and clinical risk factors [3-8]. The chance of VBAC is not only important as a direct measure of outcome but also as an indirect measure of maternal morbidity: Major maternal morbidity is lowest in women who have VBAC (morbidity 0.2 percent), higher in women who undergo ERCD (morbidity 0.8 percent), and highest in women who have a repeat cesarean delivery after a failed TOLAC (morbidity 3.8 percent) .
Although a TOLAC calculator or model can predict the probability of vaginal birth, which is a key concern of women contemplating TOLAC versus ERCD, a variety of other factors also influence a woman's decision regarding route of delivery. These factors are not addressed by calculators and are discussed in detail elsewhere. (See "Choosing the route of delivery after cesarean birth", section on 'Shared decision-making'.)To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:
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- RISK FACTORS PREDICTIVE OF TOLAC SUCCESS AND FAILURE
- MFMU Network calculator for use at entry to prenatal care
- MFMU Network calculator for use at admission for delivery
- SELECTED PREDICTION MODELS
- Shared decision-making model
- VBAC score at admission for delivery model
- Smith model
- Model for preterm pregnancies
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- SUMMARY AND RECOMMENDATIONS