Maternal morbidity associated with skin incision type at cesarean delivery in obese patients: a systematic review

Aim: To describe the relationship between cesarean skin incision type and postoperative wound complications (WCs) in obese pregnant patients. Materials & methods: MEDLINE (PubMed and OVID), Embase, Scopus, Web of Science Core Collection, Cochrane Library and ClinicalTrials.gov databases were used for publication search. Selection criteria consisted of articles studying pregnant patients with BMI ≥30 kg/m2 undergoing cesarean delivery and assessing the effect of skin incision type on postoperative maternal outcomes. Results: Ten publications met criteria for a systematic review of a total of 2946 patients. The transverse skin incision was associated with a lower rate of WC compared with the vertical skin incision. The pooled risk ratio for WCs was 0.47 (95% CI: 0.37–0.58; p < 0.00001). Conclusion: Transverse skin incision may be preferable to vertical skin incision at cesarean delivery in pregnant patients with obesity as it may be associated with a lower rate of WCs. PROSPERO registration ID: CRD42020151106

WCs were more common in pregnant patients with vertical skin incisions when compared with the transverse skin incisions, according to four studies that demonstrated a significant difference [21,24,25]. However, after adjusting for confounders, only Thornburg et al. found a statistically significant difference in WC rates between the two types of incisions [24]. The incidence of WCs in vertical incision groups varied from 14.6 to 55.8%, higher than the transverse incision groups, where the incidence varied from 7.6 to 21.1%. Our pooled analysis of eight studies showed that the transverse incision was associated with a reduced risk of developing WCs from CD (relative risk [RR] = 0.47, 95% CI: 0.37-0.58; p < 0.00001) when compared with vertical incision (Figure 2).
Five studies reported that vertical type incisions are associated with higher estimated blood loss to compare with transverse type incision [22,23,[25][26][27][28]; however, only three of those have reached statistically significant differences. Similarly, five studies stated that the transfusion rates were higher in the vertical group when compared with transverse group incision [21][22][23]26,27]; however, none of the respective studies reached statistical significance after adjusted comparison.
The length of hospital stay after delivery was reported in seven studies, with no difference between the vertical and transverse incision groups [21][22][23]25,[27][28][29]. Total operative time was longer in those with a vertical skin incision; only three of the five studies reporting this notion demonstrated a statistically significant difference (Table 2) [22,23,28]. Interestingly the Dias et al. study reported very prolonged operative times compared with all of the included studies (97 ± 31 vs 143 ± 41) [28]. This study was performed in two maternity hospitals of Scotland, in women with very severe obesity (BMI ≥40 kg/m 2 ); this is in contrast with the rest of the studies, which have been performed in the USA. The results of this study may also represent slightly different CD techniques used in the United Kingdom. However, prolonged operative time did not increase the WC rate in either group for the Dias et al. study (22.2 vs 27.7%) [28].     (9) 19 (44) 43 (100) 29 (67) Walton et al. There was a trend that high transverse and suprapannicular incisions are associated with a lower risk of WCs compared with low transverse and infrapannicular incisions described in Walton et al. and Dias et al., respectively [28,29]; however, there was no statistically significant difference between the groups.

Discussion
Our main finding was that there is a lower risk of WCs in obese pregnant patients undergoing CD with a transverse skin incision compared with a vertical skin incision (RR = 0.47, 95% CI: 0.37-0.58; p < 0.00001). The results of our study coincide with findings described by Mccurdy et al. where vertical incisions were associated with a RR of 2.07 (95% CI: 1.61-2.67) for WCs compared with transverse incisions; however, significant possible confounders were present [30].
Multiple techniques have been studied to diminish the risk of infectious complications among pregnant patients undergoing CD, including adjunctive intravenous azithromycin to standard antibiotic prophylaxis for c-section in labor or after membrane rupture [31], vaginal preparation with povidone-iodine before cesarean section and applying negative-pressure wound dressing [32]. However, neither adjunction of azithromycin nor vaginal cleansing was investigated regarding prevention infections complications in obese parturients. Application of a negative wound dressing technique demonstrated no benefit in preventing surgical site infection in the obese population [32].
Other investigators addressed the influence of surgical technique on the risk of CD surgical site infection. Low transverse type of skin incision, or Pfannenstiel, or infrapannicular in obese parturient performed under pannus irrespective of the distance from the pubic bone poses significant technical difficulties and remains an issue of debate due to the presence of the subpannicular skin fold. In light of the above, a midline vertical skin incision is more frequently suggested for obese patients [21,33]. This is despite the higher risk of postoperative pain, superficial and fascial wound dehiscence, and postoperative atelectasis associated with midline vertical skin incisions [25].
High transverse skin incision theoretically reduces WCs because a higher abdominal wall incision avoids the need to incise through the pannus and has the added advantage of transverse incision such as good tensile strength. High transverse skin incision in obese parturient or suprapannicular, describes transverse incision performed above the pannus or suprapannicular. Since pannus retraction is not necessary, less thoracic compression and resultant hypotension are noted. High transverse skin incisions are also associated with reduced postoperative pain, lower rates of dehiscence and the possible risk of infection or bleeding [29]. Despite the aforementioned research, insufficient definitive guidance is available to assist obstetricians in the selection of the best incision type to use for obese patients undergoing CD.
Given the observed increase in the risk of WCs with the use of vertical skin incisions, physicians and researchers must attempt to identify further interventions and modifications to the commonly used incisions, including innovative surgical techniques, which can reduce the overall postoperative morbidity in CD [14].
In a national anonymous survey of obstetrics and gynecology (OB/GYN) physicians, when Smid et al. assessed the preferences of obstetricians regarding cesarean incision practices in morbidly obese pregnant patients, the responders stated a preference for Pfannenstiel incision with a taping of the pannus [34]. Another multicenter anonymous survey regarding women's preference and concerns for cesarean skin incision among pregnant with class III obesity showed that patients prioritize immediate maternal and fetal safety over other concerns including cosmetic outcome [35].
There is potential for reduction of post-CD WCs through surgical techniques such as high transverse incision and suprapannicular incisions described in Walton et al. and Dias et al., respectively [28,29]. Both authors Walton et al. and Dias et al. observed a trend showing a reduction of WC with high transverse and suprapannicular type of skin incision when compared with low transverse and infrapannicular, respectively [28,29]; however, the difference did not reach statistical significance. These data demonstrate the necessity for further investigation of best skin incision techniques in obese parturients.
Our review's primary strength is that our investigation is a robust systematic review to compare different cesarean skin incision types and evaluate their postoperative effects among obese pregnant patients. Our systematic review utilized several databases to ensure proper coverage of the topic. The search strategy was maximally simplified and transparent, which makes it easily replicable. Additionally, we strictly followed the inclusion criteria that allowed us to focus on the research topic and include only those articles that describe the association between the type of skin incision and WCs in the obese obstetric population. Two independent reviewers performed screening of abstracts. We included only articles available in full text. All of these approaches provide reliable estimates about the effects of incision type on WCs in obese obstetric patients.
Our analysis has several inherent limitations because of the limited available literature addressing this topic. Nine of the ten studies which met the inclusion criteria were retrospective cohort studies. Only one RCT met the inclusion criteria. The predominance of retrospective cohort studies used lowers the level of evidence for this review. We were unable to compute pooled estimates for the cohort studies without access to individual patients' data. The specific incision technique and outcome definitions were heterogeneous and varied somewhat among the different studies. A half of the reviewed studies has not reported whether prophylactics antibiotics were utilized, which makes generalizability of results limited. Finally, a significant limitation of any retrospective cohort drove review of literature is in type of patient selection. Decision strategies insofar as the choice of the incision are a limitation. Nonetheless, our review is important because its analysis permits the development of a steppingstone for a robust understanding of this topic.

Conclusion
In conclusion, transverse skin incision may be preferable to vertical skin incision in pregnant patients with obesity as it may be associated with lower rates of WCs. Further scientific evaluation of our conclusions and correlations necessitates a prospective randomized trial.

Future perspective
Our vision is that more RCT studies will be performed to describe the best skin incision type for cesarean section in obese patients. Also, more RCTs investigating different types of transverse skin incisions will appear, allowing us to perform systematic reviews and meta-analysis to describe the association between supra and infrapinnacular incision type and WCs in obese patients with CD.

Executive summary
• Insufficient definitive guidance is available to assist obstetricians in the selection of the best incision type to use for obese pregnant patients undergoing cesarean delivery (CD). • Our systematic review of the literature is consistent with other publications in that transverse skin incision may be preferable to vertical skin incision at CD in pregnant patients with obesity as it may be associated with a lower rate of wound complications. • Further investigation of best skin incision techniques in obese parturients during CD is still needed.

Supplementary data
To view the supplementary data that accompany this paper please visit the journal website at: www.future-science.com/doi/suppl Financial & competing interests disclosure HN Moussa is a member of the Editorial Board of Future Science OA. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.
No writing assistance was utilized in the production of this manuscript.

Open access
This work is licensed under the Creative Commons Attribution 4.0 License. To view a copy of this license, visit http://creativecomm ons.org/licenses/by/4.0/