Improving a non-invasive way to monitor contractions during labor

Kirsten Thijssen defended her PhD thesis at the Department of Electrical Engineering on February 22nd. Her research was completed at Máxima Medical Center and Eindhoven University of Technology.

Uterine contractions are a key part of childbirth, but they can temporarily reduce oxygen supply to the fetus. During high-risk childbirth, monitoring of contractions is crucial to ensure safety for mother and unborn child. However, traditional monitoring techniques can be affected by maternal movements, or they are quite invasive. For her PhD thesis, Kirsten Thijssen measured the electrical activity from the uterus using non-invasive electrohysterography and considered its technological development and clinical implementation moving forward.

Uterine activity (UA) is usually monitored using a technique known as external tocodynamometry (TOCO). This is effectively a pressure sensor that is placed over the area with the strongest contractions, and it measures contraction frequency. However, accuracy is affected by the movements of the mother and obesity.

An alternative monitoring approach is an intra-uterine pressure catheter (IUPC) to measure contraction strength. However, IUPC is invasive and unpleasant for the mother. There are also risks associated with it, such as increased chances of bleeding and the potential requirement for a blood transfusion.

Due to these drawbacks with IUPC, suboptimal monitoring using TOCO has been the norm for decades, and the importance of UA monitoring has been overlooked in clinical practice.

Enter EHG!

To address the issues with other monitoring techniques, electrohysterography (EHG) is a promising non-invasive alternative. In EHG, a sensor is placed on the mother’s stomach where it measures electrical activity from the contracting uterus. The EHG method is based on prototypes developed by Eindhoven University of Technology in collaboration with Máxima MC.

For her thesis, Thijssen looked at ways to improve the development and clinical implementation of EHG as a new way to monitor UA.

First check with EHG

First, Thijssen conducted a validation study in which laboring women were simultaneously monitored with EHG and TOCO. The technique IUPC was used for reference measurements.

“EHG demonstrated significantly higher sensitivity to uterine contractions in comparison to TOCO,” says Thijssen. “Importantly, the accuracy of EHG remained unaffected by obesity, whereas the sensitivity of TOCO decreased.”

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