Severe maternal and neonatal morbidity after attempted operative vaginal delivery

Background: Operative vaginal delivery is a critical tool in reducing primary cesarean delivery, but declining operative vaginal delivery rates and concerns about provider skill necessitate a clear understanding of risks. These risks are ambiguous because most studies compare outcomes of operative vaginal delivery with that of spontaneous vaginal delivery rather than outcomes of cesarean delivery in the second stage of labor, which is usually the realistic alternative.

Objective: This study aimed to compare severe maternal and neonatal morbidity by mode of delivery of patients with a prolonged second stage of labor who had a successful operative vaginal delivery, a cesarean delivery after failed operative vaginal delivery, or a cesarean delivery without an operative vaginal delivery attempt.

Study design: We used a population-based database to evaluate nulliparous, term, singleton, vertex live births in California between 2007 and 2012 of patients with prolonged second stage of labor. Birth certificates and the International Classification of Diseases, Ninth Revision, Clinical Modification coded diagnoses and procedures were used for ascertainment of exposure, outcome, and demographics. Exposure was mode of delivery of patients who had any operative vaginal delivery attempt vs cesarean delivery without operative vaginal delivery attempt. The outcomes were severe maternal morbidity and severe unexpected newborn morbidity, defined using established indices. Anticipating that the code for prolonged second stage of labor would represent only a fraction of true operative vaginal delivery candidates, a secondary analysis was conducted removing this restriction to explore granular outcomes in a larger cohort with unsuccessful labor. Multivariable logistic regression was used to compare outcomes by mode of delivery adjusted for measured confounders. Sensitivity analyses were done excluding patients with combined vacuum-forceps-assisted delivery and birthweight of >4000 g.

Results: A total of 9239 births after prolonged second stage of labor were included, where 6851 (74.1%) were successful operative vaginal deliveries, 301 (3.3%) were failed operative vaginal deliveries, and 2087 (22.6%) were cesarean deliveries without operative vaginal delivery attempts. Of successful operative vaginal deliveries, 6195 (90.4%) were vacuum assisted and 656 (10.6%) were forceps-assisted. Of failed operative vaginal deliveries where operative vaginal delivery type was specified, 83 (47.4%) were vacuum assisted, 38 (21.7%) were forceps-assisted, and 54 (30.9%) were combined vacuum-forceps-assisted. Of note, all 54 combined vacuum-forceps-assisted operative vaginal delivery attempts that we identified failed. The outcomes of patients with failed operative vaginal delivery differed from those with successful operative vaginal delivery, such as higher rates of comorbidities, use of combined operative vaginal delivery, and birthweight of >4000 g. Successful operative vaginal delivery was associated with reduced severe maternal morbidity (adjusted odds ratio, 0.55; 95% confidence interval, 0.39-0.78) without a difference in severe unexpected neonatal morbidity (adjusted odds ratio, 0.99; 95% confidence interval, 0.78-1.26). In contrast, failed operative vaginal delivery was associated with increased severe maternal morbidity (adjusted odds ratio, 2.14; 95% confidence interval, 1.20-3.82) and severe unexpected neonatal morbidity (adjusted odds ratio, 1.78; 95% confidence interval, 1.09-2.86). In addition, findings were similar in the secondary analysis of 260,585 patients with unsuccessful labor.

Conclusion: In this large cohort of nulliparous, term, singleton, vertex births, successful operative vaginal delivery was associated with a 45% reduction in severe maternal morbidity without differences in severe unexpected neonatal morbidity compared with cesarean delivery after prolonged second stage of labor. Operative vaginal delivery infrequently failed and was associated with a 214% increase in severe maternal morbidity and a 78% increase in severe unexpected neonatal morbidity; furthermore, combined operative vaginal deliveries were major contributors to this, as all combined operative vaginal deliveries failed. Optimization of operative vaginal delivery success rates through means such as improved patient selection, enhanced provider skill, and discussions against combined operative vaginal delivery could reduce maternal and neonatal complications.