Misleading Wording: Vertical vs. Low Transverse Incisions

Recently, we discussed cesarean incisions in "obese" women, and specifically the pros and cons of a low transverse (side-to-side) incision vs. a vertical (up-down) incision.

As we noted before, for many years doctors were taught that doing an incision under an obese woman's belly fat ("pannus" in medical jargon) made it prone to infection because of the "bacteriologic cesspool" (yes, actual quote) found in the warm, moist conditions in that area.  Many were therefore taught to do a vertical incision in very fat women to lower the risk for wound complications.

However, some studies show a greatly increased risk for wound complications/blood loss with vertical incisions in obese women.  Yet to this day, many still cling to this teaching, despite a lack of support in the medical literature for it.  

Just after my post on the topic was published, a new study on the subject came out.  Here's what the abstract says (my emphasis):

After controlling for confounding factors, no difference in wound complication based on type of skin incision was apparent. The type of skin incision does not appear to be associated with wound complications in the obese parturient; however, larger studies would be needed to confirm this finding.

Sure makes it sound like a vertical incision is just as good as a low transverse one, right?  But look more closely at the full text of the study and the picture begins to change.

What The Study Really Shows

In the study, the number of vertical incisions was n=25, whereas the number of low transverse incisions was much higher, n=213.  The authors note that this was not enough to conclusively decide which incision was better, and that bigger trials were needed.  Very true.

Although the abstract gives lip service to this, the phrasing in the abstract makes it sound like vertical incisions did not result in worse outcomes, but that they needed larger studies to confirm that.  

But the thing is, the study did find worse outcomes with vertical incisions.  5 of the 25 vertical incisions (or 20%) experienced a problem with wound separation, as opposed to 22 out of 213 (or 10%) of the low transverse incisions.

So in the study, vertical incisions had twice the rate of wound separation, but because of the small number of vertical incisions, this difference did not rise to statistical significance.  

The authors were quite forward with this information in their conclusion:

We found that vertical skin incisions are associated with increased odds of postoperative wound separation, although this difference did not reach statistical significance. Although many variables factor into a surgeon’s decision on what type of skin incision to perform, the results of our study do not support the use of vertical skin incisions to reduce wound complications among obese women at the time of cesarean delivery.

That doesn't sound like what the abstract was implying, does it? Too bad the editors of the journal did not see fit to word the abstract more clearly.  They should have acknolwedged that there was no statistical significance, yes, but that there was a strong trend towards worse outcomes with vertical incisions, and that the study was underpowered to detect a statistically significant difference.

They did acknowledge the need for larger studies, but in the context of this abstract's wording it sounded like they needed larger studies to confirm that vertical was just as safe ─ when that's not at all what the authors said in the study.

Final Thoughts

OBs are very busy people and they often do not have time to read the full text of every journal article they run across.  Many just go by the conclusion of the abstracts.  Unfortunately, this abstract gives the mistaken impression that vertical incisions have outcomes just as good as low transverse incisions, when what data we have does not support this.  

A more definitive study is needed, one with a large enough sample to confirm or deny whether vertical incisions are associated with poorer outcomes.  All our research so far suggests that they are, but what we need is access to a really large database that records maternal BMI, types of incision used, and tracks post-op complications thoroughly. Perhaps the MFMU database? Researchers, are you listening?

In the meantime, I suppose it's some comfort that apparently, most women of size who have cesareans are getting low transverse incisions.  YAY.  We need to do less cesareans in women of size, period, but at least most of the cesareans in this group are being done with low transverse incisions.  Small comfort, but I'll take it.

But the stories I hear from women of size suggest that even so, too many obese women are STILL being subjected to the greater risks and ugliness of vertical incisions.  In fact, in this study, 11% of obese women were still being subjected to vertical incisions.  That's too many.  Sometimes, vertical incisions can be needed, but not one out of every ten sections.

Vertical incisions don't "prevent" infection or improve outcome in any way; research suggests it actually increases blood loss, operative time, and wound complications; it increases the likelihood of a classical uterine incision underneath (which is associated with more morbidity short- and long-term); and it creates an ugly scar that negatively impacts a fat woman's sense of self. 

Considering the number of cesareans done every year on women of size, it's time someone accessed a large database and debunked this outdated teaching once and for all.  Until that is done, however, doctors need to acknowledge the clear trend in the research and not use vertical incisions routinely in women of size. 

Am J Perinatol. 2011 Nov 21. Type of Skin Incision and Wound Complications in the Obese Parturient. McLean M, et al. PMID: 22105439

We examined the relationship between type of skin incision at time of cesarean delivery and postoperative wound complications in the obese parturient. Women with a body mass index (BMI) of greater than 29 who had undergone cesarean delivery at The University of North Carolina were identified from the Pregnancy, Infection and Nutrition study. Inpatient and outpatient medical records were reviewed for maternal demographics as well as intrapartum and intraoperative characteristics. The exposure of interest was type of incision, classified as vertical or transverse. The primary outcome was wound complication, defined as partial or complete wound separation. Logistic regression analysis was used to create a final model of risk factors for wound complications while controlling for potentially confounding variables. From 1998 to 2005, 238 women with a BMI greater than 29 who underwent cesarean delivery were identified. Of these 238 women, a vertical skin incision was performed in 25 (11%) and a transverse skin incision in 213 (89%). The overall incidence of wound complications in this group was 13%. BMI was associated with wound complications (p less than 0.01). After controlling for confounding factors, no difference in wound complication based on type of skin incision was apparent. The type of skin incision does not appear to be associated with wound complications in the obese parturient; however, larger studies would be needed to confirm this finding. Increased BMI is associated with a higher rate of wound complications.