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MS WordPerinatologist Corner - C.E.U/C.M.E. Modules
Vaginal Birth After Cesarean
Sponsored by The Indian Health Service Clinical Support Center
3. Risk factors
What are the risks of vaginal birth after cesarean?
Case scenario #2
E. J. is a 27 y/o G3P2 at 41 weeks gestation who presents in early labor to your facility, where cesarean capability is available. She has a history of two prior cesareans. Her first baby, who is now 2 years old, was born at term by cesarean because "he was too big for me to push out". That child weighed "over 9 pounds" at birth. Her second child, now almost 1 year old, was born at term by repeat cesarean delivery after she experienced an arrest of dilation and descent at 6 cm. This baby also weighed over 9 pounds. She wishes to have a normal delivery this time. She is having mild irregular contractions and your exam reveals her cervix to be 1-2 cm dilated, 80% effaced, with the vertex at a -3 station and intact membranes. You estimate the fetal weight clinically to be over 9 pounds. The fetal monitor strip is reassuring.
How would you counsel her?
How safe is a trial of labor after cesarean?
Overall, 60-80% of women who choose V.B.A.C. will achieve a vaginal birth. If the prior indication for cesarean was a non-recurrent one (e.g., breech presentation, severe preeclampsia), the success rate is over 90%, whereas if the original indication was dystocia, the success rate is generally reduced to 50- 70%. Success is also enhanced for the current birth if a prior V.B.A.C. has occurred and if the woman is admitted in active labor (>4 cm dilation). There is also some evidence that an inter-pregnancy of greater than 18 months is associated with fewer complications of a subsequent T.O.L.A.C. The advantages of a successful V.B.A.C. are a lesser need for transfusion, fewer postpartum infections, a shorter hospital stay, and no increased perinatal morbidity, at a lower cost, if the attempt is successful.
McMahon in a longitudinal population-based study of 6,138 women in Canada, found that the incidence of major complications (uterine rupture, hysterectomy, operative injury) was 1.6% vs. 0.8% for a trial of labor (T.O.L.) versus an elective repeat cesarean (E.R.C.) (RR=1.8). Sixty-five per cent of the complications occurred in the women who failed to deliver vaginally (OR=1.7). In this study there was no difference in the rate of minor complications (puerperal fever, transfusion, wound infection).
Gregory, in a retrospective discharge data study of 66,856 births after prior cesarean in California, found 392 uterine ruptures (0.43%). The relative risk of T.O.L. vs. E.R.C. was 1.88.
Rageth, in another retrospective database report from Europe (n=29,046), found a uterine rupture rate of 0.4 vs. 0.2% for T.O.L. vs. E.R.C. (RR=2.1) and a perinatal mortality rate of 0.5 vs. 0.3% (RR=1.7). Compared to women with successful V.B.A.C., those who failed their T.O.L. had an RR of uterine rupture of 8.11.
In a meta-analysis of 15 studies of prior cesarean involving 47,682 women, Mozurkewich found a uterine scar disruption rate of 3.9% and 3 maternal deaths in the T.O.L .group versus no deaths and a disruption rate of 1.6% in the E.R.C. group. The corresponding perinatal death rates were 0.6 vs. 0.3% (OR=1.7).
Lydon-Rochelle in another retrospective database analysis from Washington state involving 20,095 women, found a uterine rupture rate of 1.6 per 1000 for women with E.R.C., and 5.2/1000 for women who labored (RR=3.3). If labor was induced with oxytocin or mechanical means the rupture rate was 7.7/1000 (RR=4.9), but if labor was induced with prostaglandins the rupture rate was 24.5/1000 (RR=15.6).
The conclusion of almost all these large studies is that while T.O.L.A.C. is a relatively safe procedure and should be continued, it has a small but definite risk, especially if the T.O.L. is not successful. The take home message is that, while trying to take into account patient preference, candidates for TOLAC should be chosen carefully in order to labor only those with the best chance of success and the least chance of an adverse outcome.
The preponderance of evidence suggests that most patients who have had a low-transverse uterine incision from a previous cesarean delivery and who have no contraindications for vaginal birth are candidates for a trial of labor.
ACOG Selection criteria useful in identifying candidates for VBAC:
- One previous low-transverse cesarean delivery
- Clinically adequate pelvis
- No other uterine scars or previous rupture
- Physician immediately available throughout active labor capable of monitoring labor and performing an emergency cesarean delivery
- Availability of anesthesia and personnel for emergency cesarean delivery
ACOG Circumstances under which trial of labor should not be attempted
- Previous classical or T-shaped incision or extensive transfundal uterine surgery
- Previous uterine rupture
- Medical or obstetric complication that precludes vaginal delivery
- Inability to perform emergency cesarean delivery because of unavailable surgeon, anesthesia, sufficient staff, or facility
- Two prior uterine scars and no vaginal deliveries
American College of Obstetricians and Gynecologists. Vaginal birth after previous cesarean delivery. ACOG Practice Bulletin No. 54. Obstet Gynecol 2004;104:203-12.
Factors found not to increase the rupture risk
Factors found not to increase the rupture risk included epidural analgesia, fetal macrosomia, a prior successful V.B.A.C., an unknown scar type, and prior cesarean for dystocia.
Based on the findings from several retrospective studies, it may be reasonable to offer a trial of labor to women in the following other specific obstetric circumstances: gestation beyond 40 weeks, previous low-vertical Incision, and twin gestations.
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