Maternal Morbidity Rates Relative to Length of Labor in a Multiethnic Patient Population [ID: 1337798]

INTRODUCTION: Prolonged induction of labor is associated with increased morbid maternal outcomes. Induction of labor length varies by institution and labor management. The objective of this study was to determine the risk of morbid outcomes increasing hours of labor induction in a multiethnic tertiary care center. METHODS: We conducted a retrospective cohort study on patients undergoing scheduled induction of labor from June 2020 to May 2021 at a tertiary care center. Nulliparous singleton term pregnancies with intact membranes who had an initial cervical dilation less than 3 were included. Length of labor induction was defined as first intervention to birth. Morbid outcomes included suspected intraamniotic infection (IAI), postpartum hemorrhage (PPH), and cesarean birth. Multivariable logistic regressions were performed relative to the length of labor. RESULTS: Two hundred sixty-seven patients were included in our study, with 18.0% Asian American/Pacific Islander, 6.4% Black/non-Hispanic, 20.2% Hispanic, 32.6% White/non-Hispanic, 17.6% multiracial/other, and 5.2% unknown. The median labor length was 28.5 hours (interquartile range 21.2–38.5). The rates of IAI was 22%, PPH 12%, and cesarean birth 22%. For every hour of labor, there was 1.04 increased odds of IAI, 1.08 odds of cesarean birth, and 1.05 odds of PPH after adjusting for confounders ( P <.01). When comparing White versus non-White patients, there were no differences in labor length (28.4 hours versus 28.6 hours, P =.46) and no differences in IAI, PPH, and cesarean. CONCLUSION: For each hour of labor, the risk of IAI, PPH, and cesarean birth increased by 4%, 8%, and 5%, respectively. Characteristics contributing to this association may be multifactorial and suggest labor management should aim for an expedient birth.