Some care providers discourage epidurals in VBAC moms fearing that it will mask the symptoms of uterine rupture (namely abdominal pain) and delay diagnosis resulting in a poor outcome for baby and to a lesser extent, mom Other care providers suggest or even require VBAC moms to have an epidural so that a cesarean can quickly take place if needed. Which philosophy does the evidence support?
Review of 14 VBAC studies
I recently came across a study entitled “The Role of Epidural Anesthesia in Trial of Labor” (Johnson, 1990) that reviewed 14 VBAC studies. Johnson found among scarred women who ruptured, a greater percentage of women with epidurals reported abdominal pain than women without epidurals.
- 5 of 14 (35.7%) patients with an epidural who ruptured had abdominal pain.
- 4 of 23 (17.4%) patients without an epidural who ruptured had abdominal pain.
Interestingly, only 22% of the women who ruptured in that study reported abdominal pain and Johnson concluded, “Thus abdominal pain is an unreliable sign of complete uterine rupture.” But is it? 69% of women in Zwart (2009) reported abdominal pain. (I write about Zwart here and here.)
One difference between the studies is Zwart included significantly more scarred moms than Johnson: 26,000 versus 10,976. The second different is that Zwart also included 332,000 unscarred women representing 93% of the sample population.
Unscarred moms, uterine rupture, and abdominal pain
I’m curious if the reason why Zwart reported such a high level of abdominal pain was because it included so many unscarred moms. I wonder if unscarred moms are more likely to report pain and if so, why would that be. Zwart combines the symptoms for scarred and unscarred rupture into one chart. If they broke that chart out by scarred vs. unscarred rupture symptoms, would we see any major differences? Generally, unscarred rupture does more damage to the uterus and is more likely to result in an infant death (Zwart, 2009), so maybe because there is more damage, women report more abdominal pain?
Most common UR symptom: fetal heart tone abnormalities
I checked out eMedicine’s article “Uterine Rupture in Pregnancy” and was fascinated to learn that several studies concur with Johnson. They also found that abdominal pain is reported at a much lower rate than fetal distress/ abnormal fetal heart tones:
…sudden or atypical maternal abdominal pain occurs more rarely than do decelerations or bradycardia. In 9 studies from 1980-2002, abdominal pain occurred in 13-60% of cases of uterine rupture. In a review of 10,967 patients undergoing a TOL, only 22% of complete uterine ruptures presented with abdominal pain and 76% presented with signs of fetal distress diagnosed by continuous electronic fetal monitoring. [This is the Jonhson study.]
Moreover, in a study by Bujold and Gauthier, abdominal pain was the first sign of rupture in only 5% of patients and occurred in women who developed uterine rupture without epidural analgesia but not in women who received an epidural block. (Bujold E, Gauthier RJ. Neonatal morbidity associated with uterine rupture: what are the risk factors?. Am J Obstet Gynecol. Feb 2002;186(2):311-4). Thus, abdominal pain is an unreliable and uncommon sign of uterine rupture. Initial concerns that epidural anesthesia might mask the pain caused by uterine rupture have not been verified and there have been no reports of epidural anesthesia delaying the diagnosis of uterine rupture.
A 2012 study out of the UK (Fitzpatrick, 2012) also reported that 76% of uterine ruptures were accompanied by fetal heart rate abnormalities in comparison to 49% reporting abdominal pain.
ACOG’s stance on epidurals
It’s important to note that ACOG does support the use of epidurals in VBACs:
Epidural analgesia for labor may be used as part of TOLAC, and adequate pain relief may encourage more women to choose TOLAC (109, 110). No high quality evidence suggests that epidural analgesia is a causal risk factor for an unsuccessful TOLAC (44, 110, 111). In addition, effective regional analgesia should not be expected to mask signs and symptoms of uterine rupture, particularly because the most common sign of rupture is fetal heart tracing abnormalities (24, 112).
Remember that fetal heart tracing abnormalities were detected in 76% of the ruptures in Johnson ad 67% of the ruptures in Zwart.
I couldn’t find any mention of epidurals masking rupture pain in the Guise 2010 Evidence Report, but found that the Johnson study was excluded from their report because “No full-text paper, opinion or letter with no data.” Interesting.
Uterine rupture symptoms
A list of uterine rupture symptoms and their frequency per Medscape’s article on uterine rupture.
- “80% Prolonged deceleration in fetal heart rate or bradycardia
- 54% Abnormal pattern in fetal heart rate
- 40% Uterine hyper-stimulation
- 37% Vaginal bleeding
- 26% Abdominal pain
- 4% Loss of intrauterine pressure or cessation of contractions”
A couple notes. One, abdominal pain is not a consistent or reliable symptom of UR. Two, there is a level of interpretation that goes into diagnosing abnormal fetal heart tones even among people who have extensive medical training.
Additional symptoms that I have collected from other sources include:
- Baby’s head moves back up birth canal
- Bulge in the abdomen or under the pubic bone (where the baby may be coming through the tear in the uterus)
- Uterus becomes soft
- Shoulder pain
Risks and benefits of epidurals
As with every option available to you regarding birth, it’s always good to be knowledgeable on the risks and benefits of epidurals so you can make an informed choice. Three excellent resources are this article by Sarah Buckley MD, the PubMed Health Epidural Fact Sheet and this review of epidural research by the Cochrane Library.
Take home message
The limited information available tells us that epidurals do not mask abdominal pain from uterine rupture.
The most common symptom of uterine rupture is fetal distress diagnosed by fetal heart rate abnormalities.
Epidurals may be used during a trial of labor after cesarean per ACOG.
As always, if you can offer further research or perspective on this topic, please leave a comment. Our knowledge is constantly growing and we can only work with the best information available to us now. Who knows what future research will tell us?