REPORTING FROM THE PREGNANCY MEETING
DALLAS (FRONTLINE MEDICAL NEWS) – No clear winner emerged in a first-ever randomized controlled trial comparing Pfannenstiel with vertical incisions for women with obesity having cesarean delivery, though enrollment difficulties limited study numbers, with almost two-thirds of eligible women declining to participate in the surgical trial.
At 6 weeks postdelivery, 21.1% of women who had a vertical incision experienced wound complications, compared with 18.6% of those who had a Pfannenstiel incision, a nonsignificant difference. This was a smaller difference than was seen at 2 weeks postpartum, when 20% of the vertical incision group had wound complications, compared with 10.4% of those who had a Pfannenstiel, also a nonsignificant difference. Maternal and fetal outcomes didn’t differ significantly with the two surgical approaches.
”We were unable to demonstrate a difference in the primary or secondary outcomes in women with class III obesity who received Pfannenstiel versus vertical skin incision,” said Caroline C. Marrs, MD , presenting the study results at the meeting sponsored by the Society for Maternal-Fetal Medicine.
Though there had been several observational studies comparing vertical with Pfannenstiel incisions for cesarean delivery in women with obesity, no randomized, controlled trials had been conducted, and observational study results were mixed, said Dr. Marrs.
Each approach comes with theoretical pros and cons: For women who have a large pannus, the incision site may lie in a moist environment with a low transverse incision, and oxygen tension may be low. However, a Pfannenstiel incision usually will have better cosmesis than will a vertical incision, and generally will result in less postoperative pain.
On the other hand, said Dr. Marrs, vertical incisions can provide improved exposure of the uterus during delivery, and the moist environment underlying the pannus is avoided. However, wound tension may be higher, and subcutaneous thickness is likely to be higher than at the Pfannenstiel incision site.
The study, conducted at two academic medical centers, enrolled women with a body mass index (BMI) of at least 40 kg/m2 at a gestational age of 24 weeks or greater who required cesarean delivery. Consenting women were then randomized to receive Pfannenstiel or vertical incisions.
Women who had clinical chorioamnionitis, whose amniotic membranes had been ruptured for 18 hours or more, or who had placenta accreta were excluded. Also excluded were women with a private physician and those desiring vaginal delivery, said Dr. Marrs, a maternal-fetal medicine fellow at the University of Texas Medical Branch, Galveston.
The study’s primary outcome measure was a composite of wound complications seen within 6 weeks of delivery, including surgical site infection, whether superficial, deep, or involving an organ or tissue space; cellulitis; seroma or hematoma; and wound separation. Other maternal outcomes tracked in the study included postoperative length of stay, transfusion requirement, sepsis, readmission, and death.
Cesarean-specific secondary outcomes included operative time and time from skin incision to delivery, estimated blood loss, and any incidence of hysterectomy through a low transverse incision. Neonatal outcomes included a 5-minute Apgar score of less than 7, umbilical cord pH of less than 7, and neonatal ICU admissions.
Dr. Mars said that the goal enrollment for the study was 300 patients, to ensure adequate statistical power. However, they found enrollment a challenge, with low consent rates during the defined time period from October 2013 to May 2017. They shifted their statistical technique to a Bayesian analysis, taking into account the estimated probability of treatment benefit.
Using this approach, they found a 59% probability that a Pfannenstiel incision would lead to a lower primary outcome rate – a better result – than would a vertical incision. This result just missed the predetermined threshold of 60%, said Dr. Marrs.
Of the 789 women who met the BMI threshold for eligibility assessment, 420 (65%) who passed the screening declined to participate. Of those who consented to participation, an additional 137 women either withdrew consent or failed further screening, leaving 50 women who were randomized to the Pfannenstiel arm and 41 who were randomized to the vertical incision arm.
Baseline characteristics were similar between groups, with a mean maternal age of 30 years in the Pfannenstiel group and 28 years in the vertical incision group. Gestational age at delivery was a mean of 37 weeks in both groups, and mean BMI was 48-50 kg/m2.
Most patients (80%-90%) had public insurance. Diabetes was more common in the Pfannenstiel group (48%) than in the vertical incision cohort (32%). Just over 40% of patients were African American.
Two women in the Pfannenstiel group and three in the vertical incision group did not receive the intended incision. After accounting for patients lost to follow-up by 6 weeks, 43 women who received Pfannenstiel and 38 women who received vertical incisions were available for full evaluation.
Dr. Marrs said that the study, the first randomized trial to address this issue, had several strengths, including its being conducted at two sites with appropriate stratification for the sites. Also, an independent data safety monitoring board and two chart reviewers helped overcome some of the limitations of a surgical study, where complete blinding is impossible.
The Bayesian analysis allowed ascertainment of the probability of treatment benefit despite the lower-than-hoped-for enrollment numbers. The primary weakness of the study, said Dr. Marrs, centered around the low consent rate, which led to a small study that was prematurely terminated.
“It’s difficult to enroll women in a trial that requires random allocation of skin incision, due to their preference to choose their own incision. A larger trial would likewise be challenging, and unlikely to yield different results,” said Dr. Marrs.
Dr. Marrs reported no conflicts of interest.
SOURCE: Marrs CC et al. Am J Obstet Gynecol. 2018 Jan;218:S29 .