Abstract
Understanding the mechanisms of uterine contractions during pregnancy is especially important in predicting the onset of labor and thus in forecasting preterm deliveries. Preterm birth can cause serious health problems in newborns, as well as large financial burdens to society. Various techniques such as electromyography (EMG) and magnetomyography (MMG) have been developed to quantify uterine contractions. However, no widely accepted method to predict labor based on electromagnetic measurement is available. Therefore, developing a biophysical model of EMG and MMG could help better understand uterine contractions, interpret real measurements, and detect labor. In this work, we propose a multiscale realistic model of uterine contractions during pregnancy. At the cellular level, building on bifurcation theory, we apply generalized FitzHugh-Nagumo (FHN) equations that produces both plateau-type and bursting-type action potentials. At the tissue level, we introduce a random fiber orientation model applicable to an arbitrary uterine shape. We also develop an analytical expression for the propagation speed of transmembrane potential. At the organ level, a realistic volume conductor geometry model is provided based on magnetic resonance images of a pregnant woman. To simulate the measurements from the SQUID Array for Reproductive Assessment (SARA) device, we propose a sensor array model. Our model is able to reproduce the characteristics of action potentials. Additionally, we investigate the sensitivity of MMG to model configuration aspects such as volume geometry, fiber orientation, and pacemaker location. Our numerical results show that fiber orientation and pacemaker location are the key aspects that greatly affect the MMG as measured by the SARA device. We conclude that sphere is appropriate as an approximation of the volume geometry. The initial step towards validating the model against real MMG measurement is also presented. Our results show that the model is flexible to mimic the limited-propagation magnetic signature during the emergence and decay of a uterine contraction.
Highlights
The clinical importance of modeling contractions of pregnant uterus lies in better understanding the mechanisms of normal and preterm births
We introduced a variation of the FitzHugh-Nagumo equations to generate both plateau-type and bursting-type action potentials
We introduced a realistic anatomical model for the volume conductor geometry based on the magnetic resonance images of a pregnant woman
Summary
The clinical importance of modeling contractions of pregnant uterus lies in better understanding the mechanisms of normal and preterm births. Preterm birth, which occurs before 37 weeks of gestation, has potential to result in serious health problems to preterm infants. In addition to health problems, preterm birth causes huge financial costs to families and society [1]. It is urgent to understand the mechanisms under which uterine contractions lead to preterm birth. The uterus provides a safe environment for developing fetus, which is later expelled through intense contractions. These contractions are primarily regulated by the uterine electrical activities [2, 3]. In [5], the authors demonstrate that two mechanisms, action potential propagation and calcium wave propagation, contribute to intercellular communication
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