From the Journals

Predictive model estimates likelihood of failing induction of labor in obese patients



A predictive model estimates when a pregnant woman with obesity is at increased or decreased risk of failing induction of labor and requiring cesarean section, reported researchers from the University of Cincinnati and Cincinnati Children’s Hospital Medical Center.

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The ten variables included in the model were prior vaginal delivery; prior cesarean delivery; maternal height, age, and weight at delivery; parity; gestational weight gain; Medicaid insurance; pregestational diabetes; and chronic hypertension, said Robert M. Rossi, MD, of the university and associates, who developed the model.

“Our hope is that this model may be useful as a tool to estimate an individualized risk based on commonly available prenatal factors that may assist in delivery planning and allocation of appropriate resources,” the investigators said in a study summarizing their findings, published in Obstetrics & Gynecology.

The researchers conducted a population-based, retrospective cohort study of delivery records from 1,098,981 obese women in a National Center for Health Statistics birth-death cohort database who underwent induction of labor between 2012 and 2016. Of these women, 825,797 (75%) women succeeded in delivering after induction, while 273,184 (25%) women failed to deliver after induction of labor and instead underwent cesarean section. The women included in the study had a body mass index of 30 or higher and underwent induction between 37 weeks and 44 weeks of gestation.

The class of obesity prior to pregnancy impacted the rate of induction failure, as patients with class I obesity had a rate of cesarean section of 21.6% (95% confidence interval, 21.4%-21.7%), while women with class II obesity had a rate of 25% (95% CI, 24.8%-25.2%) and women with class III obesity had a rate of 31% (95% CI, 30.8%-31.3%). Women also were more likely to fail induction if they had received fertility treatment, if they were older than 35 years, if they were of non-Hispanic black race, if they had gestational weight gain or maternal weight gain, if they had pregestational diabetes or gestational diabetes, or if they had gestational hypertension or preeclampsia (all P less than .001). Factors that made a woman less likely to undergo cesarean delivery were Medicaid insurance status or receiving Special Supplemental Nutrition Program for Women, Infant and Children (SNAP WIC) support.

Under the predictive model, the receiver operator characteristic curve (ROC) had an area under the curve (AUC) of 0.79 (95% CI, 0.78-0.79), and subsequent validation of the model using a different external U.S. birth cohort dataset showed an AUC of 0.77 (95% CI, 0.76-0.77). In both datasets, the model was calibrated to predict failure of induction of labor up to 75%, at which point the model overestimated the risk in patients, Dr. Rossi and associates said.

“Although we do not stipulate that an elective cesarean delivery should be offered for ‘high risk’ obese women, this tool may allow the provider to have a heightened awareness and prepare accordingly with timing of delivery, increased staffing, and anesthesia presence, particularly given the higher rates of maternal and neonatal adverse outcomes after a failed induction of labor,” said Dr. Rossi and colleagues.

Martina Louise Badell, MD, commented in an interview, “This is well-designed, large, population-based cohort study of more than 1 million obese women with a singleton pregnancy who underwent induction of labor. To determine the chance of successful induction of labor, a 10-variable model was created. This model achieved an AUC of 0.79, which is fairly good accuracy.

Dr. Martina L. Badell is an assistant professor of gynecology and obstetrics in the division of maternal-fetal medicine at Emory University in Atlanta.

Dr. Martina L. Badell

“They created an easy-to-use risk calculator as a tool to help identify chance of successful induction of labor in obese women. Similar to the VBAC [vaginal birth after cesarean] calculator, this calculator may help clinicians with patient-specific counseling, risk stratifying, and delivery planning,” said Dr. Badell, a maternal-fetal medicine specialist who is director of the Emory Perinatal Center at Emory University, Atlanta. Dr. Badell, who was not a coauthor of this study, was asked to comment on the study’s merit.

The authors reported no relevant financial disclosures. Dr. Badell had no relevant financial disclosures. There was no external funding.

SOURCE: Rossi R et al. Obstet Gynecol. 2019. doi: 10.1097/AOG.0000000000003377.

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