A look at the data on hysterotomy closure – how many layers?
Given that cesarean delivery is the second most common surgery performed in this country, it is somewhat surprising that as a profession we can’t seem to settle on what the best way to do it is. We argue about how we should open, what we should close on the way out, and how we should close these layers. Some have even argued that we shouldn’t even enter the peritoneal cavity in doing the surgery, which leads to a radically different approach.
Of all the variations on this surgery, one element that has been up to a great deal of discussion is how many layers we should close the uterus in. Like many things in surgical and clinical technique, the answer to this question seems to have changed over time, and has even gone back and forth. When I was training in the late 90’s, we were closing the uterus with a single layer of chromic gut suture. Towards the end of my training, we slid towards a double layer of gut, and now we are seeing some movement back towards a single layer, but now with polygalactin 910 (Vicryl or Polysorb.)
There have been two separate areas of concern with how many layers we should close with. One of these concerns have been the immediate effects of how we close the uterus on patient factors such as immediate postop pain, infection rates, blood loss, and surgical time. The second concern has been the effect of closure technique on uterine rupture rate in subsequent VBAC attempts.
Like all areas of controversy, there are surgeons that are passionate on either side. There are also groups of non-physicians that have taken strong stands on this issue, which to surgeons can seem a little out of place given the heterogeneity of the data and the variable interpretations of that data.
So let’s take a look at the data, and see if it is clear enough to really come down on one side or the other. There are three major studies that examine this question, all of which are either retrospective cohort or case-control studies.
The impact of a single-layer or double-layer closure on uterine rupture. Bujold E, Bujold C, Hamilton E, Harel F, Gauthier R. Am J Obstet Gynecol 2002; 186:1326-30.
This often-quoted paper is a large study of women undergoing trial of labor between 1988 and 2000 at the St-Justine Hospital in Montreal, Quebec. The study is a large case control comparing women who experienced uterine rupture (23 cases) with those who did not (1957 controls), for a rupture rate in the studied population of 1.2%.
All closures were either single or double layered closures using locked continuous chromic catgut suture. Uterine ruptures were defined as defects of the entire thickness of the uterine wall. Both inductions and spontaneous labors were included. Prostaglandins were used in only 6 total cases. Foley catheters were commonly used when cervical ripening was needed.
The only factor clearly associated with uterine rupture was a single-layer uterine closure in the cesarean prior to the TOL (Adjusted OR 3.95, 95% CI 1.35 – 11.49, p = 0.012) TOL within 2 years of previous cesarean was nearly associated with uterine rupture (OR 2.31, 95% CI 0.97-5.52, p = 0.059.) Birth weight, epidurals, foley catheter ripening, previous vaginal deliveries, and previous VBAC all were not associated with uterine rupture.
Summary result: Single layer closure with locked chromic was associated with uterine rupture with an odds ratio of almost 4, over double layer closure.
Uterine rupture, perioperative and perinatal morbidity after single-layer and double-layer closure at cesarean delivery. Durnwald C, Mercer B. Am J Obstet Gynecol 2003; 189:925-9.
This was a non-concurrent prospective cohort study of all women who had a G1 cesarean delivery followed by a G2 VBAC trial of labor at Metrohealth Medical Center in Cleveland, Ohio from 1989 to 2001. The two cohort groups were women who had single layer closure (n = 183) and women who had double layer closures (n = 340.)
Uterine rupture was defined as a full thickness rupture, similar to the 2002 Bujold study. Unlike the Bujold study, which used locked chromic gut suture, 99% of deliveries in this study were done with continuous unlocked Polygalactin 910 (Vicryl) suture.
Single layer and double layer closure groups were demographically similar in age, gestational age at time of TOL, labor duration, frequency of protracted labor, use of internal monitors, meconium staining, incidence of cesarean for fetal distress vs. arrest of labor. Frequency of labor induction was similar between groups, at 20% and 16% in the two groups (similar at p = 0.21.)
Uterine rupture occurred 4 times (0.7% of all cases). There was no statistical difference between the frequency of rupture between the two groups, and all four of the ruptures occurred in the double-layer closure group.
Double-layer closure was associated with longer operating times (52 vs 46 minutes, p < 0.0001) and greater blood loss (690 ml vs 646 ml, p < 0.0001), and longer postoperative stays (2.0 vs 1.8 days, P < 0.0001). There were no differences in hemorrhage rates, transfusion rates, endometritis.
Summary result: Single layer closure with unlocked vicryl was not associated with increased risk of uterine rupture over double layer closure.
Single versus double-layer uterine incision closure and uterine rupture. Gyamfi C, Juhasz G, Gyamfi P, Blumenfeld Y, Stone J. J Matern Fetal and Neonat Medicine 2006; 19(10): 639-643.
This was also a non-concurrent prospective cohort study, consisting of VBAC TOL cases at Mount Sinai SOM in New York City between Jan 1996 and Dec 2000. Similar to the Durnwald study, the population were split into two cohorts – women with single layer closures (n=35) and women with double layer closures (n=913).
The two groups were similar in age, race, gestational age, and frequency of induction. They were different in time interval between deliveries (mean 38 months in the double layer group vs 26 months in the single layer group, P = 0.001). The vast majority of hysterotomies were closed with chromic catgut suture, locking unspecified.
The majority of inductions were performed with prostaglandins, predominantly misoprostol. This differed this study from the other two studies, which as a rule did not use prostaglandins in
Uterine rupture occurred 3 of the 35 single layer closure cases (8.6%) versus 12 out of 913 double layer cases (1.3%), p=0.015.
Summary result: Single layer closure was associated with much higher uterine rupture rate than double layer, notably using misoprostol for cervical ripening in inductions.
Each study is different in design and execution, and so naturally each study had a different result. Bujold et al showed that with chromic suture, single layer closures were associated with a higher frequency of uterine rupture in VBAC than double layer closures. Durnwald found somewhat different results, failing to show a difference in rupture rates between groups, but using Vicryl suture instead of chromic gut. Gyamfi again showed a difference when using chromic gut, but this time at an even higher odds ratio, but notably using misoprostol in inductions.
Each study also had weaknesses. First, all of them are retrospective, and none are randomized. The lack of randomization is likely not a great problem though, because suture choice is a surgeon preference, and unlikely to be associated with another risk factor for uterine rupture and therefore create bias. The Durnwald study also suffered from a lack of power, having only 543 patients to look at a very rare outcome (uterine rupture) in comparison to the 1,980 patients in the Bujold study. While Durnwald was powered to find the adjusted 4x difference noted in the Bujold study, it was inadquately powered to find a smaller difference. This leaves us to question whether the different result was due to chance alone.
The biggest difference between Durnwald and Bujold was the difference in suture, and the technique used to close the uterus. Bujold used chromic suture, which loses 50% of its strength within 7 days, versus Vicryl which holds its strength much longer, taking 17 days to lose 50% of its strength. It is very plausible that this difference could lead to significant difference in wound healing, and thus differences in scar strength. This can be particularly true in cases complicated by uterine infection, which can greatly accelerate the degradation of chromic, as it is destroyed by an inflammatory reaction, in comparison to Vicryl which degrades via hydrolysis. The fact that the Durnwald cases did not lock the suture may also be important, as locking the suture decreases the blood flow to the incision, which is ultimately why surgeons choose to do it. In fact, many surgeons would never consider not locking a hysterotomy, given the brisk bleeding that can occur if a bleeder gets loose in the postoperative period.
Durnwald also has the benefit of being a cohort study, which is typically a somewhat stronger design than a case control design, used by Bujold.
Gyamfi demonstrated a huge difference in rupture rates between single and double layer closure, but as in his study misoprostol was used in induction, it is difficult to apply this data to current practice where we never use miso with VBACs.
So what should we do? I think that if one likes to use chromic suture and is willing to give up the few additional minutes in surgery, the most evidence based practice would be to do a double-layer closure. If one is using Vicryl, one could justifiably use a single layer closure, and likely benefit from the shorter operating room time and associated morbidity.
What do you do?