Towards improving uterine electrical activity modeling and electrohysterography: ultrasonic quantification of uterine movements during labor.

The electrohysterogram is a potential new tool for diagnosing preterm labor. Parameters from the electrohysterogram may be influenced by uterine movement. An observational study was performed quantifying uterine movement during labor as a step towards improving electrohysterogram analysis for predicting preterm labor. The uterine wall was continuously tracked by ultrasound imaging during first stage of labor while an accelerometer recorded external abdominal accelerations in six women. A cyclic cranial-caudal movement of the uterine wall, caused by maternal respiration, was observed. This is reported and quantified for the first time. Average frequency, amplitude, and peak speed were 0.27 ± 0.07 Hz, 0.68 ± 0.84 cm, and 1.04 ± 1.20 cm/s, respectively. The accelerometer signal correlated with uterine movement and therefore can possibly provide a reference for removing movement-induced artifacts. There is a need to model and measure the effect of uterine movement on the electrohysterogram parameters and make measurements more robust to movement artifacts.

Ultrasound analysis of the uterine wall movement for improved electrohysterographic measurement and modeling.

During pregnancy, analysis of the electrohysterogram (EHG), which measures the uterine electrical activity, can provide a fundamental contribution for the assessment of uterine contractions and the diagnosis of preterm labor. However, several aspects concerning uterine physiology and its link with EHG measurements are still unclear. As a consequence, the EHG is not yet part of the clinical practice. There is general consensus that modeling and analysis of the EHG can be improved only by understanding and integrating the main properties of the uterine physiology at different levels, e:g:, cellular, tissue, and organ, and of different nature, e:g:, electrical, mechanical, and structural. In this study, we use transabdominal ultrasound (US) measurements to investigate the mechanical changes that the uterus undergoes during pregnancy under the effect of contractions. We refer to this measurement as mechanohysterogram. Analysis of the mechanohysterogram highlights, for the first time, two phenomena that can influence EHG signal interpretation, namely, changes in uterine wall thickness during contractions and respiration-induced uterine wall movements. Our results suggest that these phenomena can affect the interpretation of the EHG and should therefore be taken into account for accurate modeling and assessment of the uterine electrical activity.