Newer technology aims to offer a new way of monitoring contractions through uterine contraction monitoring and FHR monitoring with transabdominal uterine electromyography (EMG) and external fetal electrocardiogram (fECG) monitoring.
Traditional labor monitoring systems, such as the tocodynamometer (TOCO), can't boast similar features. However, each system does have pros and cons. Providers should think carefully about the difference between TOCO and EMG and choose which system is best for each patient.
It's always best to make an informed decision, so here's a closer look at the difference between TOCO and EMG monitoring during labor.
Traditional External Labor Monitoring
Traditional labor monitoring has been achieved through both external and internal means. External labor monitoring typically relies on ultrasound technology to measure and record FHR and TOCO, a tocotransducer technology, to measure changes in abdominal tension caused by uterine contractions.
The benefits of external monitoring are that it's a familiar, widely used technology that's generally reliable, easy to navigate, and does allow for some patient movement. Although the reading can be temporarily interrupted, the monitors can be left in place to allow for patient ambulation when connected to an ambulatory fetal monitor, such as GE HealthCare's Mini Telemetry System.
However, TOCO methods do have significant drawbacks—namely, they can be unreliable in certain patient populations, such as those with a high BMI. Additionally, TOCO technology cannot measure contraction intensity or resting tone, readings can be obstructed by movement, and the belts holding the transducers can be uncomfortable for patients.
Traditional Internal Labor Monitoring
Internal labor monitoring—which uses a fetal scalp electrode to measure FHR and an intrauterine pressure catheter (IUPC) for contractions—aims to solve some of the unreliability issues with external monitoring.
There are benefits to internal monitoring, especially from a provider standpoint, because internal monitors provide superior, reliable measurements for both FHR and uterine activity. Internal monitoring can also be used when external monitoring isn't possible, such as for patients with a high BMI. And, because an IUPC measures the pressure within the uterus, it provides an accurate measurement of the actual intensity or resting tone of the contractions.
However, there are still drawbacks to this method. Some of the major cons to consider with internal monitoring include the fact that it requires some membranes to be ruptured for effective placement. Although the risk is small, internal monitors are also associated with an increased risk of infection, according to a study published by the American Journal of Obstetrics and Gynecology.1 Additionally, because the cervix must be adequately dilated to allow for placement, improper placement of internal monitors can cause placental trauma.
Patient comfort and satisfaction can also be significantly impacted with internal monitoring, as it can restrict the patient to their bed. And once the monitors have been placed (not always a pleasant experience without an epidural), the internals can become dislodged due to factors such as the baby's movement, patient movement, or provider placement.
Modern Labor Monitoring
Let's take a closer look at more modern technology—specifically, noninvasive fECG and EMG monitoring.
Transabdominal uterine EMG measures the electrical activity of the uterus to interpret contraction patterns. Because the uterus is a smooth muscle, when it contracts, those muscles will release electrical bursts that can be measured by surface electrodes placed on the skin. This is the same technology used in ECG monitoring, which measures the heart's electrical activity when it contracts. Fetal ECG and EMG, then, can be used together for external labor monitoring for both FHR and contractions. This is done most commonly by electrodes that stick directly to the patient's abdomen.
The benefits of wireless monitoring are considerable. "The Novii allows freedom of movement, which is so helpful for dealing with labor pain, especially if a patient does not want to have an epidural," notes Michelle Bader, CNM with Valley OB in Michigan. "It's useful when using hydrotherapy for labor comfort measures, as well. I wish we had a unit for every laboring patient if they require continuous monitoring."
As Bader referenced, some EMG/ECG monitoring systems, such as the Novii Wireless Patch System, are waterproof and can be left on during hydrotherapy. Additionally, because the systems are entirely wireless, the patient also has increased mobility. In one clinical trial study of the system, 95% of mothers reported it was easier to change positions with the Novii and 85% found it easier to walk around during labor as compared to TOCO monitoring.2
Like other adhesive patch sensors, a small percentage of users have reported skin irritation from this new technology, and this new method for FHR may not work for all situations.
EMG/ECG systems are also noninvasive—so they can safely be used in term patients in all labor stages—while still offering improved accuracy comparable to TOCO methods. Unlike TOCO external monitoring, EMG can accurately measure the frequency and timing of uterine contractions on high BMI patients as it is not affected by adipose tissue, allowing it to be utilized without belts and wires on nearly all patient populations.
How to Choose the Right Monitoring System
When choosing the right labor monitoring system for your patients, it's important to consider factors including the following:
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Reliability and accuracy
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Patient preference and experience
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Staff training for the new technology introduction
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Connectivity capabilities for wireless technologies
Overall, research published by the American Journal of Perinatology supports the move toward advancing EMG and ECG technology.3 This reliable, accurate technology features considerable benefits for patients and providers alike. Consider upgrading your systems to bring some comfort and much-needed support to your laboring moms.
References:
- Harper LM, Shanks AL, Tuuli MG, et al. The risks and benefits of internal monitors in laboring patients. American Journal of Obstetrics and Gynecology. 2013;209(1):38.e1-38.e6. doi:10.1016/j.ajog.2013.04.001
- Monson M, Heuser C, Einerson BD, Esplin I, Snow G, Varner M, Esplin,MS. Evaluation of an external fetal electrocardiogram monitoring system: a randomized controlled trial. Am J Obstet Gynecol. 2020 Aug;223(2):244.e1-244.e12. doi:10.1016/j.ajog.2020.02.012. Epub 2020 Feb 20. PMID: 32087146; PMCID: PMC8842851.
- Thijssen KMJ, Vlemminx MWC, Westerhuis MEMH, et al. Uterine monitoring techniques from patients' and users' perspectives. AJP Reports. 2018;8(3):e184-e191. doi:10.1055/s-0038-1669409