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Poster session II Clinical obstetrics, diabetes, labor, medical-surgical-disease, physiology/endocrinology, prematurity: Abstracts 237 - 386| Volume 208, ISSUE 1, SUPPLEMENT , S126, January 01, 2013

277: Defining an abnormal first stage of labor: does the 95th percentile make sense?

      Objective

      By tradition, surpassing the 95th percentile (%ile) in the 1st stage of labor defines dystocia. However, these women may deliver vaginally, avoiding unnecessary cesarean delivery (CD) and raising questions about definitions of abnormal. Therefore, we sought to determine a threshold for defining abnormal labor associated with adverse maternal & neonatal outcomes.

      Study Design

      Retrospective cohort of all consecutive women admitted ≥37.0 weeks gestation from 2004-2008 who reached the 2nd stage of labor. Detailed information was collected on maternal demographics, labor progress, & neonatal outcomes. The 90th, 95th, & 97th %ile for progress in 1st stage of labor was determined specific for parity & labor onset. Women with 1st stage above & below each centile were compared. Maternal outcomes were CD in 2nd stage, operative delivery, prolonged 2nd stage, post-partum hemorrhage, & maternal fever. Neonatal outcomes were a composite of: admission to level 2 or 3 nursery, 5-minute Apgar ≤3, shoulder dystocia, cord pH ≤7.1, & cord base excess ≤−12.

      Results

      5,385 were included in the analysis. Exceeding 90th, 95th, & 97th %ile in the 1st stage of labor was associated with increased risks of prolonged 2nd stage, maternal fever & the composite neonatal outcome, although the risk of other outcomes were similar. Compared to women in the 90-94th centile, women exceeding the 95th %ile in labor were more likely to experience maternal fever (relative risk (RR) 1.63, 95% confidence interval (CI) 1.08-2.46) & shoulder dystocia (RR 1.86, 95% CI 1.13-3.06) but had similar risk of the composite neonatal outcome (RR 1.28, 95% CI 0.97-1.71).