Rates of severe maternal and neonatal morbidity were similar among superobese women undergoing primary cesarean delivery versus a trial of labor, most often ending in vaginal delivery. Researchers say a prospective clinical trial is needed to determine whether one method of birth is superior to the other in mothers who are superobese.
According to Alexander Butwick, MBBS, FRCA, MS, among women who are superobese, rates of cesarean delivery are particularly high (≥50%), but little has been known about how delivery mode affects perinatal and neonatal outcomes. Dr. Butwick, who presented the findings at the 2016 annual meeting of the Society for Obstetric Anesthesia and Perinatology (abstract 01-02), is associate professor in the Department of Anesthesiology, Perioperative and Pain Medicine at Stanford University School of Medicine, in California.
Over the years, clinicians have observed that obesity is associated with an increased risk for obstetric, perinatal and anesthetic morbidities. Obese pregnant women are at an increased risk for gestational diabetes, preeclampsia, operative delivery, postpartum infection and venous thromboembolism.
“Obstetricians are uncertain whether superobese women can undergo a trial of labor for intended vaginal delivery as opposed to planned cesarean section. This may be because rates of maternal and neonatal morbidity associated with each of these approaches for delivery is poorly understood,” Dr. Butwick said.
In the current retrospective analysis, researchers compared maternal and neonatal morbidities among women who were superobese who underwent a trial of labor (n=1,918) or a planned cesarean delivery (n=775) in California between 2007 and 2011. For their analysis, investigators relied on birth record data as well as maternal and neonatal hospitalization data.
To be included in the analysis, women had to have a pre-pregnancy body mass index (BMI) of 50 kg/m2 or higher and have delivered at or greater than 36 weeks gestation. The researchers excluded women with multiple fetuses and women who underwent a trial of labor after a previous cesarean delivery. The rate of vaginal delivery in the labor group was 85%.
Women who underwent primary cesarean delivery had a slightly lower BMI (55 vs. 57 kg/m2; P<0.001), but they were more likely to be nulliparous (61% vs. 32%; P<0.001), have some form of hypertensive disease associated with pregnancy (38% vs. 26%; P<0.001), have gestational diabetes (21% vs. 18%; P=0.06) or have preexisting diabetes (8% vs. 3%; P<0.001).
The frequency of severe maternal morbidity or death was low in women who underwent a trial of labor (0.6%) and women with a primary cesarean delivery (1.4%), a difference that was not statistically significant.
The frequency of neonatal morbidity was low in women who had a trial of labor (0.9%) versus those who underwent a primary cesarean delivery (1.6%), and this difference was not statistically significant. Neonatal morbidity was defined as at least one of the following: neonatal ICU admission, a birth injury, a baby being ventilated more than six hours, a seizure or serious neurologic dysfunction.
Dr. Butwick pointed out that the numerators in the study were very low, which made it difficult for researchers to adequately adjust for confounders. “We can conclude [from this study] that there are likely to be very low rates of severe maternal morbidity among women who are superobese, but it is difficult for us to adequately or accurately quantify the increased risk of morbidity when we compare those who undergo a trial of labor with those who undergo primary cesarean delivery,” said Dr. Butwick. He believes a large prospective study is needed to compare outcomes in superobese women undergoing planned cesarean delivery versus those undergoing expectant management intending vaginal delivery.
In a question-and-answer session following the presentation, Richard Smiley, MD, PhD, chief of obstetric anesthesia at NewYork-Presbyterian Hospital/Columbia University Medical Center, in New York City, applauded the study. “It is impressive that you even have a case series of [almost] 3,000 superobese patients being delivered,” said Dr. Smiley.
Dr. Smiley agreed that a randomized trial is needed and said it is “unusual” to see worse neonatal outcomes from cesarean deliveries. “Unless they did these C-sections early, it is pretty unusual to see worse neonatal outcomes from a C-section, despite all the political reasons we think we shouldn’t do C-sections,” Dr. Smiley said. He wondered whether some of the cesarean deliveries were thus indicated for fetal reasons, which would affect the data.
Dr. Butwick said whether the cesarean delivery was indicated for a maternal, obstetric or fetal indication was important, but the data sources for the analysis did not include indications for delivery mode.