VBAC
| Rationale for Compliance |
Evidence Grade |
|
|---|---|---|
| Compared with one cesarean birth, accumulating cesarean surgeries imposes increasing risks of (see pp. 48S–56S for risks of an individual cesarean): | ||
| • adhesions (Makoha, 2004; Seidman, 1994): Known risks of adhesions include chronic pain, the possibility of causing intestinal obstruction, and increased risk of injury during subsequent surgeries. | Quality: | A |
| Quantity: | A | |
| Consistency: | A | |
| • cesarean scar ectopic pregnancy (Jurkovic, 2003; Maymon, 2004). | Quality: | A |
| Quantity: | B | |
| Consistency: | A | |
| • placenta previa (Getahun, 2006; Makoha, 2004; MCA, 2004). | Quality: | A |
| Quantity: | A | |
| Consistency: | A | |
| • placenta accreta (Silver, 2004): Placenta accreta is associated with high rates of catastrophic and life-threatening outcomes, including hysterectomy, severe hemorrhage and the complications that accompany severe hemorrhage such as disseminated intravascular coagulation, need for additional surgery, and maternal death (Forna, 2004; Makoha, 2004; Selo-Ojeme, 2005; Silver, 2004). | Quality: | A |
| Quantity: | A | |
| Consistency: | A | |
| • placenta previa/accreta b (Chattopadhyay, 1993; Makoha, 2004; Miller, 1997; Silver, 2004; To, 1995). | Quality: | A |
| Quantity: | A | |
| Consistency: | A | |
| • hemorrhage requiring transfusion c (Makoha, 2004; Silver, 2004). | Quality: | A |
| Quantity: | A | |
| Consistency: | A | |
| • hysterectomy (Kwee, 2006; Makoha, 2004; Selo-Ojeme, 2005; Silver, 2004). | Quality: | A |
| Quantity: | A | |
| Consistency: | A | |
| • bladder injury d (Makoha, 2004; Phipps, 2005). | Quality: | A |
| Quantity: | B | |
| Consistency: | A | |
| • neonatal respiratory complications (Seidman, 1994). | Quality: | C |
| Quantity: | C | |
| Consistency: | NA* | |
| Compared with planned vaginal birth, elective repeat cesarean section increases the risk of: | ||
| • maternal infection (Guise, 2003). | Quality: | C |
| Quantity: | B | |
| Consistency: | A** | |
| • hemorrhage requiring transfusion c (Guise, 2003; Macones, 2005; Mozurkewich, Hutton 2000). | Quality: | A |
| Quantity: | A | |
| Consistency: | B | |
| • hysterectomy (Guise, 2003; Mozurkewich, 2000). | Quality: | B |
| Quantity: | A | |
| Consistency: | B (One SR reported fewer hysterectomies; the other reported similar rates.) | |
| • neonatal respiratory complications (Loebel, 2004). | Quality: | B |
| Quantity: | C | |
| Consistency: | NA* | |
| Vaginal birth appears to be protective against symptomatic scar rupture (Lieberman, 2001; Macones, 2005; Smith, 2004). | Quality: | B |
| Quantity: | A | |
| Consistency: | A | |
| The incidence of symptomatic uterine scar rupture can be 4 per 1,000 planned vaginal births or fewer e (Gonen 2006; Guise, 2003; Landon et al., 2004; Lieberman, 2004; Loebel, 2004; McMahon, 1996; Mozurkewich, 2000; Smith, 2004). | Quality: | A |
| Quantity: | A | |
| Consistency: | A | |
| Planned repeat cesarean does not eliminate the possibility of symptomatic uterine scar rupture (Lydon-Rochelle, 2001; Mozurkewich, 2000). | Quality: | B |
| Quantity: | A | |
| Consistency: | A | |
| Systematic reviews that calculate absolute excess risk (the arithmetic difference between the two rates) of symptomatic uterine scar rupture with planned VBAC compared with planned repeat cesarean report values of 2.3 and 2.7 per 1,000 (Guise, 2003; Mozurkewich, 2000). This means that 270–435 elective cesareans would be needed to prevent one scar rupture (number needed to treat). | Quality: | A |
| Quantity: | A | |
| Consistency: | A | |
| The perinatal mortality rate associated with symptomatic uterine scar rupture during VBAC labor is extremely low: | ||
| • The perinatal mortality rate associated with symptomatic uterine scar rupture during planned vaginal birth ranges from 1.5 to 4.0 per 10,000 VBAC labors (Guise, 2003; Landon et al., 2004; Lydon-Rochelle, 2001; Mozurkewich, 2000; Smith 2002). | Quality: | A |
| Quantity: | A | |
| Consistency: | NA to reporting a range of rates | |
| • The excess risk of perinatal death associated with symptomatic uterine scar rupture compared with planned cesarean section ranges from 1.4 to 2.6 per 10,000 planned VBACs (Guise, 2004; Landon et al., 2004). To put this number into perspective, the excess risk of losing the pregnancy associated with having mid-trimester amniocentesis is 60 per 10,000 (Seeds, 2004). This means from 3,846 to 7,142 elective cesareans would be needed to prevent one perinatal death. | Quality: | A |
| Quantity: | A | |
| Consistency: | NA to reporting a range of rates | |
| Conclusions in the two studies examining the issue differ on whether a decision-to-incision interval of less than 20 minutes improves outcomes in cases of symptomatic uterine scar rupture (Guise, 2003). The study finding that it did included cases in which the infant required resuscitation but sustained no morbidity. If these cases are removed from consideration, only one case of asphyxia remains among the babies with later emergent delivery. | Quality: | B |
| Quantity: | B | |
| Consistency: | C | |
| Modifiable factors may increase the risk of symptomatic uterine scar rupture. These include: | ||
| • induction of labor with oxytocin (Delaney, 2003; Guise, 2003; Landon et al., 2004; Lieberman, 2001; Locatelli, 2004; Lydon-Rochelle, 2001; Macones, 2005; Smith, 2004). | Quality: | B |
| Quantity: | A | |
| Consistency: | C f | |
| • induction of labor with PGE2 (Delaney, 2003; Guise, 2003; Locatelli, 2004; Lydon-Rochelle, 2001; Macones 2005; Smith, 2004). | Quality: | B |
| Quantity: | A | |
| Consistency: | C f | |
| • induction of labor with misoprostol (Lieberman, 2001; Plaut, 1999; Wing, 1998). | Quality: | B |
| Quantity: | B | |
| Consistency: | A | |
| • augmentation of labor (Gonen, 2006; Landon et al., 2004; Macones, 2005; Lieberman, 2001). | Quality: | A |
| Quantity: | A | |
| Consistency: | B g | |
| • possibly single-layer uterine closure h (Bujold, 2002; Durnwald, 2003). | Quality: | B |
| Quantity: | B | |
| Consistency: | C i | |
| Adverse outcomes in planned vaginal births occur mostly in women having cesarean sections (Landon et al., 2004; Loebel, 2004; McMahon, 1996; Phipps, 2005). This argues for policies that maximize likelihood of vaginal birth. | Quality: | A |
| Quantity: | A | |
| Consistency: | A | |
| Three out of four women or more in an unselected population who plan VBAC should have a vaginal birth. This implies that VBAC rates lower than 70% are due to modifiable factors. | ||
| • Many studies and systematic reviews report VBAC rates around 75% in an unselected population, and rates as high as 87% are reported (Gonen, 2006; Guise, 2003; Landon et al., 2004; Lieberman, 2004; Locatelli, 2004; Loebel, 2004; Macones, 2005; Smith, 2002). | Quality: | A |
| Quantity: | A | |
| Consistency: | NA to reporting a range of rates | |
| • Rates of 95% have been reported in women with optimal profiles for VBAC (Guise, 2003). | Quality: | A |
| Quantity: | NA to reporting a rate | |
| Consistency: | NA to reporting a rate | |
| • Rates as high as 81% have been reported among women with no prior vaginal birth (Lieberman, 2004). | Quality: | A |
| Quantity: | NA to reporting a rate | |
| Consistency: | NA to reporting a rate | |
| • Even when maternal history and obstetric factors are suboptimal for VBAC, the chance of VBAC can be at least 50/50 (Guise, 2003; Landon, 2004; Macones, 2005; Rosen, 1990). | Quality: | A |
| Quantity: | A | |
| Consistency: | A | |
| Inducing labor appears to reduce the likelihood of vaginal birth (Delaney, 2003; Guise, 2003; Landon, 2004; Locatelli, 2004).j | Quality: | C |
| Quantity: | A | |
| Consistency: | A | |
A = good, B = fair, C = weak, NA = not applicable
Quality = aggregate of quality ratings for individual studies
Quantity = magnitude of effect, numbers of studies, and sample size or power
Consistency = the extent to which similar findings are reported using similar and different study designs
only 1 study
multiple studies in a SR
only 1 study in a SR
The Australian trial is being protested by Australian grassroots normal birth advocates who question the ethics of assigning healthy women to major abdominal surgery when so little new knowledge can be gained.
The authors of a case series on cesarean scar ectopic pregnancies theorized that placenta previa/accreta results when a cesarean scar implantation develops into an intrauterine pregnancy (Jurkovic, 2003).
Need for transfusion was used rather than hemorrhage because it is a more objective measure of blood loss. In addition, definitions of hemorrhage vary between vaginal birth and surgical delivery. The usual definition of hemorrhage at vaginal birth is 500 ml, whereas for surgery it is 1,000 ml. Moreover, while blood loss is hard to measure accurately in either case, it is especially so at vaginal birth.
Surgical injury at repeat cesarean is more common because of the presence of adhesions.
Studies report higher scar rupture rates, but the fact that rates this low are reported in large, unselected VBAC populations indicates that substantially higher rates are almost certainly due to modifiable factors.
Inconsistencies can probably be explained by variations in protocol and patient selection (Locatelli, 2004; Macones, 2005). For example, one study reported an increase in scar rupture with the combination of induction with oxytocin and PGE2 but not with either agent used separately (Macones, 2005).
Inconsistencies may be explained by variations in oxytocin augmentation protocols.
One study found a significant increase with single-layer closure while another did not. The trial that did not raised the issue of differences in suture material and technique between the two studies possibly affecting scar strength (Durnwald, 2003). No systematic reviews could be found addressing the issue of material and technique and scar strength in subsequent VBAC labors. Until this controversy is settled, a conservative approach would dictate using double-layer closure because many studies predating the use of single-layer closure report symptomatic scar rupture rates less than 5 per 1,000.
Inconsistencies may be explained by variations in suture material and technique.
Only one study reporting this adjusted for the fact that indications for labor induction might also increase the likelihood of cesarean section (Delaney, 2003).