Strengths and Limitations
Strengths of this study include use of a large diverse cohort, allowing for subgroup analysis and larger generalization of the results. Assessment of resting intrauterine tone is novel and addresses a quandary that is identified in clinical practice. There are several limitations to this study. First, placement of IUPC at our institution is not universal and thus the cohort is subject to selection bias. Additionally, our database only included the last 120 minutes of IUPC data, limiting our analysis to this timepoint. Due to a paucity of data on the average or “normal” resting intrauterine tone there is no established definition of elevated tone. We chose ≥ 75%, however, further investigations with larger sample sizes should be used to determine a possible threshold resting tone that is associated with uterine hypoperfusion and neonatal morbidity The majority of patients delivered vaginally and were primarily in the second stage of labor for the duration of available IUPC data. Thus, we were unable to assess the effects of elevated resting tone throughout the first stage of labor. Lastly, while the number of patients included in the study was sizable it remains underpowered for individual analysis of rare adverse events leading to the need for a composite outcome with the potential bias associated with pooling outcomes.