Variables Associated with Successful Vaginal Birth after One Cesarean Section: A Proposed Vaginal Birth after Cesarean Section Score

ABSTRACT

The objective of this study was to define the variables associated with vaginal birth after cesarean section (VBAC) and to develop a scoring system for the prediction of successful VBAC. We searched our computerized database for parturients with a history of one low-transverse cesarean section (CS) who were delivered during the year 2000. Variables were categorized according to the time period in which they were obtained: (1) first prenatal visit, (2) at the onset of labor, and (3) during labor. Univariate and multiple stepwise logistic regression models were fitted to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Of the 475 parturients with a history of one previous CS, 136 underwent elective CS and 339 underwent a trial of VBAC, of whom 82% were successful. Of the variables that can be obtained at the onset of labor, five were significantly associated with successful VBAC: abnormal presentation as the indication for the primary CS (OR, 7.4; 95% CI 2.8 to 19.2), a previous VBAC (OR, 7.2; 95% CI, 2.1 to 24.8), cervical dilation (OR, 2.5; 95% CI, 1.3 to 4.9), gestational age ≤ 41 weeks (OR, 2.8; 95% CI, 1.1 to 7.1), and lower gestational age at the primary CS (OR, 1.2; 95% CI, 1.02 to 1.4). In the proposed VBAC score, each of the four most significant variables was assigned a score ranging between 0 and 3 based on the probability for VBAC. A score ≤ 2 was associated with a success rate of 42%, a score between 3 and 6 was associated with a rate of 81%, and a score between 7 and 10 was associated with a 98% successful VBAC rate (p < 0001). The proposed VBAC score may help obstetricians when counseling their patients regarding the individual likelihood of a successful VBAC.

Cesarean delivery - VBAC - scoring system

REFERENCES

• 1 Rosen M G, Dickinson J C, Westhoff C L. Vaginal birth after cesarean: a meta-analysis of morbidity and mortality.  Obstet Gynecol. 1991;  77 465-470
• 2 Flamm B L. Vaginal birth after cesarean section. In: Flamm BL, Quilligan EJ Cesarean Section: Guidelines for Appropriate Utilization. New York; Springer-Verlag 1995: 51-64
• 3 Flamm B L, Goings J R, Liu Y, Wolde-Tsadik G. Elective repeat cesarean delivery versus a trial of labor: a prospective multicenter study.  Obstet Gynecol. 1994;  83 927-932
• 4 Mozurkewich E L, Hutton E K. Elective repeat cesarean delivery versus trial of labor: a meta-analysis of the literature from 1989 to 1999.  Am J Obstet Gynecol. 2000;  183 1187-1197
• 5 Lyndon-Rochele M, Holt V L, Easterling T R, Martin D P. Risk of uterine rupture during labor among women with prior cesarean delivery.  N Engl J Med. 2001;  345 3-8
• 6 McMahon M J, Luther E R, Bowes W A, Olshan A F. Comparison of a trial of labor with an elective second cesarean section.  N Engl J Med. 1996;  335 689-695
• 7 Hibbard J U, Ismail M A, Wang Y, Te C, Karrison T. Failed vaginal birth after a cesarean section: how risky is it? 1. Maternal morbidity.  Am J Obstet Gynecol. 2001;  184 1365-1371
• 8 Hamilton B E, Martin J A, Sutton P D. Births: Preliminary data for 2002.  Natl Vital Stat Rep. 2003;  51 1-20
• 9 Menacker F, Curtin S C. Trends in cesarean birth and vaginal birth after previous cesarean, 1991-1999.  Natl Vital Stat Rep. 2001;  49 1-16
• 10 Troyer L R, Parisi V M. Obstetric parameters affecting success in a trial of labor: designation of a scoring system.  Am J Obstet Gynecol. 1992;  167 1099-1104
• 11 Flamm B L, Geiger A M. Vaginal birth after cesarean delivery: an admission scoring system.  Obstet Gynecol. 1997;  90 907-910