The association between gestational age and maternal adverse outcomes in patients undergoing TOLAC

Abstract

Trial of labor after cesarean (TOLAC) is supported by the American College of Obstetricians and Gynecologists as a method of reducing the cesarean delivery rate. However, there is a paucity of evidence regarding the outcomes of TOLAC at preterm compared to term gestational age (GA). In other populations, preterm birth is associated with increased maternal morbidity. We hypothesized that maternal adverse outcomes would be increased in patients who undergo TOLAC prior to term. In this population-based retrospective cohort study using the U.S. vital statistics datasets on Period Linked Birth-Infant Death Data from 2014 to 2018, we compared patients who attempted TOLAC at term (37+ weeks) to preterm (23-36 weeks) GA. The primary outcome was a composite of maternal adverse outcomes (CMAO), which included maternal blood transfusion, uterine rupture, unplanned hysterectomy, or admission to the intensive care unit (ICU) as a complication of delivery. A subgroup analysis was performed and stratified by GA (23-27, 28-33, 34-36, and 37-41 weeks). Relative risks were calculated and adjusted based on differences in socio-demographic factors between the two groups. There were 455,284 patients who met inclusion criteria for the study; 39,589 were at a preterm GA and 415,695 were at a term GA. The overall CMAO was significantly higher for patients undergoing TOLAC at preterm GA (12.0 per 1,000 live births) compared to term GA (8.0 per 1,000 live births; aRR, 1.42, 95% CI, 1.29-1.56 (Table 1)). Among individual conditions within the primary composite outcome, preterm GA was associated with maternal transfusion, unplanned hysterectomy, and increased risk of admission to the ICU (Table 1). In the subgroup analysis, the rate of CMAO was highest in the 23-27 week cohort (22.8 per 1,000 live births; aRR, 2.56, 95% CI, 1.92-3.43) compared to the 28-33 week (aRR, 1.79, 95% CI, 1.50-2.15), and the 34-36 week cohort (aRR, 1.24, 95% CI, 1.10-1.39) (Table 2). In patients who underwent TOLAC, preterm GA was associated with increased maternal adverse outcomes.View Large Image Figure ViewerDownload Hi-res image Download (PPT)