Transactions of the Twenty-Fifth Annual Meeting of the Society for Maternal-Fetal Medicine
The MFMU Cesarean Registry: Factors affecting the success of trial of labor after previous cesarean delivery

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Objective

The purpose of this study was to determine which factors influence the likelihood of successful trial of labor (TOL) after 1 previous cesarean delivery (CD).

Study design

We performed a multicenter 4-year prospective observational study (1999-2002) of all women with previous CD undergoing TOL. Women with term singleton pregnancies with 1 previous low transverse CD or unknown incision were included for analysis.

Results

Fourteen thousand five hundred twenty-nine women underwent TOL, with 10,690 (73.6%) achieving successful VBAC. Women with previous vaginal birth had an 86.6% success rate compared with 60.9% in women without such a history (odds ratio [OR] 4.2; 95% CI 3.8-4.5; P < .001). TOL success rates were affected by previous indication for CD, need for induction or augmentation, cervical dilation on admission, birth weight, race, and maternal body mass index. Multivariate logistic regression analysis identified as predictive of TOL success: previous vaginal delivery (OR 3.9; 95% CI 3.6-4.3), previous indication not being dystocia (CPD/FTP) (OR 1.7; 95% CI 1.5-1.8), spontaneous labor (OR 1.6; 95% CI 1.5-1.8), birth weight <4000 g (OR 2.0; 95% CI 1.8-2.3), and Caucasian race (OR 1.8, 95% CI 1.6-1.9) (all P < .001). The overall TOL success rate in obese women (BMI ≥30) was lower (68.4%) than in nonobese women (79.6%) (P < .001), and when combined with induction and lack of previous vaginal delivery, successful VBAC occurred in only 44.2% of cases.

Conclusion

Previous vaginal delivery including previous VBAC is the greatest predictor for successful TOL. Previous indication as dystocia, need for labor induction, or a maternal BMI ≥30 significantly lowers success rates.

Section snippets

Material and methods

The cesarean registry was a 4-year observational study of the National Institute of Child Health and Human Development Maternal–Fetal Medicine Units Network designed to address clinical issues related to cesarean childbirth. The study was conducted at 19 academic medical centers; 8 centers participated throughout the study, 5 participated only during the first 2 years and 6 participated for part of the last 2 years. Data were collected for women undergoing attempted vaginal birth after cesarean

Results

During the study period (1999-2002), there were 29,661 women who had a singleton gestation at term with a history of 1 previous cesarean delivery with a transverse or unknown incision. Of these cases, 14,529 (49.0%) underwent trial of labor. Ten thousand six hundred ninety (73.6%) achieved successful VBAC, whereas 3839 (26.4%) failed a TOL. Among those 3839 cases, repeat operation was performed in 2037 (53.1%) for cephalopelvic disproportion/failure to progress dystocia, 1123 (29.3%) for

Comment

Because previous studies have indicated success rates ranging from 60% to 80%, this large multicenter observational cohort study confirms that nearly three fourths of women at term undergoing a trial of labor after previous cesarean section will achieve a successful vaginal delivery.6 Various demographic and clinical characteristics are clearly predictive of VBAC success. Among these factors, we found previous vaginal delivery including successful previous VBAC as the most significant. In our

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Supported by grants from the National Institute of Child Health and Human Development (HD21410, HD21414, HD27860, HD27861, HD27869, HD27883, HD27889, HD27905, HD27915, HD27917, HD34116, HD34122, HD34136, HD34208, HD34210, HD34136, HD40500, HD40485, HD40544, HD40545, HD40560, HD40512, HD19897, and HD36801).

Presented at the Twenty-Fifth Annual Meeting of the Society for Maternal Fetal Medicine, February 7-12, 2005, Reno, Nev.

The other members of the network are listed in the Appendix.

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