The three-dimensional spatiotemporal dynamics of human uterine contractions using electromyometrical imaging (EMMI)

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Summary/Abstract We have limited understanding of how uterine contractions develop and become sufficiently coordinated to expel the fetus at term. For example, we lack answers to basic questions about labor such as where contractions initiate, how fast contractions propagate, which regions of the uterus are active during contractions, and how these measures change as labor progresses. To address this knowledge gap, a new imaging technology, Electromyometrial Imaging (EMMI) was recently developed and validated in a translational sheep model. EMMI employs magnetic resonance imaging to acquire a subject-specific body-uterus geometry, then combines the resulting data with electrophysiological data collected from up to 256 electrodes on the abdominal surface. With EMMI, it is possible to noninvasively image the electrical activation and conduction patterns during contractions across the entire uterus in three dimensions. Preliminary data indicate that EMMI can be used to systematically characterize contractions during normal term labor in humans. Additionally, three proposed features of uterine electrical activity, termed "contraction indices", appear to correlate with time until delivery. The objectives of this proposal are to use EMMI to create a "normal term atlas" describing the 3D electrical activation patterns of human uterine contractions at high spatial and temporal resolution across labor, and to use this atlas to begin to identify contraction features associated with impending labor arrest. Aim 1 is to define the uterine electrical maturation and contraction patterns during labor in term nulliparous women. In this Aim, EMMI will be conducted on 430 nulliparous women throughout labor, and data will be analyzed from the 365 women who are anticipated to have normal term labor. This aim tests the hypothesis that at least one of the EMMI-derived uterine contraction indices can precisely reflect progression of normal term labor in nulliparous women, and can reliably differentiate the different phases of the first stage of labor. Exploratory Aim 2 will evaluate uterine electrical contraction patterns during labor in the anticipated 75 women from Aim1 who experience labor arrest. This exploratory aim will provide the basis for a future larger EMMI study to fully characterize the spatial-temporal signatures of uterine contractions in patients who develop arrested labor. In completing these two aims, this project will generate physiologically normal standards of uterine contraction indices of nulliparous women during the progress of term labor. These normal standards will permit future in-depth clinical investigations of the factors leading to dysfunctional labor. Moreover, they may, in the longer term, serve as standards for monitoring pregnancy and labor progression and assessing the effectiveness of treatment strategies to manage labor and prevent labor complications such as preterm birth, labor arrest, and postpartum hemorrhage.