What Do Contractions Look Like on a TOCO Monitor?

Monitoring uterine contractions is an essential part of childbirth, helping healthcare providers assess labor progression and ensure the well-being of both the mother and baby.

One of the most commonly used tools in labor monitoring is the tocodynamometer, or TOCO monitor. This external device tracks uterine contractions, offering a real-time view of their frequency, duration, and intensity.

Understanding how contractions appear on a TOCO monitor can provide valuable insights for both clinicians and expectant mothers, helping guide decisions throughout labor [*].

In this article, we’ll explain how contractions are measured, the different types of contraction monitors available, and how to read and interpret TOCO monitor readings.

Whether you’re a first-time parent or a healthcare professional looking for a deeper understanding, this guide will help you make sense of contraction monitoring and its role in childbirth.

How Are Contractions Measured?

Uterine contractions, the rhythmic tightening and relaxing of the uterus, play a crucial role in labor. They help to dilate the cervix and eventually push the baby through the birth canal. Measuring these contractions allows healthcare providers to track the progression of labor and respond if any complications arise [*].

Contractions are typically measured in three key ways [*]:

1. Frequency: How often the contractions occur, usually measured from the start of one contraction to the start of the next.
2. Duration: How long each contraction lasts, typically measured in seconds.
3. Intensity: The strength of the contractions, often measured in arbitrary units (AU) on external monitors or in millimeters of mercury (mmHg) with internal monitors.

Tracking these parameters helps healthcare teams understand how well the uterus is working to progress labor and when medical interventions, such as medication or cesarean delivery, might be necessary [*].

Types of Contraction Monitors

There are two main types of contraction monitors: continuous and intermittent. Both have their place in childbirth, but each serves a different purpose depending on the circumstances [*].

1. Continuous Monitors: These devices provide ongoing, real-time data on both the mother’s contractions and the baby’s heart rate. Continuous monitoring is often used in hospital settings, particularly for high-risk pregnancies, when labor is induced, or when an epidural is administered. The TOCO monitor is an example of a continuous external monitor that tracks contractions throughout labor [*].
2. Intermittent Monitors (Auscultation): This method involves checking contractions periodically using handheld devices, such as a Doppler or stethoscope. Intermittent monitoring is more common in low-risk pregnancies and home birth settings, as it allows more freedom of movement and minimizes medical intervention [*].

Because TOCO monitors are the most widely used type of contraction monitor in hospital settings, we’ll focus on how they work and how to interpret their readings.

What Is a TOCO Monitor?

A TOCO monitor, or tocodynamometer, is a device that measures uterine contractions externally. It is usually placed on the mother’s abdomen, secured with an elastic belt, and positioned over the uterine fundus, where contractions are strongest. The device detects pressure changes in the abdomen caused by uterine contractions, translating these changes into graphical and numerical data [*].

TOCO monitors provide a non-invasive way to measure the strength and frequency of contractions, making them a popular choice for routine labor monitoring. The TOCO number, which reflects the intensity of the contractions, is displayed on the monitor, helping healthcare providers determine the effectiveness of each contraction and monitor the overall progress of labor [*].

What Do Contractions Look Like on a Monitor?

When viewed on a TOCO monitor, contractions appear as wave-like peaks on a graph. Each peak represents a single contraction, and the characteristics of these peaks — such as their height and frequency — provide important information about the labor process [*]:

• Peaks: The rise in the graph represents the onset of a contraction, while the peak itself shows the contraction’s strongest point.
• Height: Taller peaks indicate stronger contractions. Mild contractions will produce lower peaks, while stronger contractions will result in higher peaks.
• Spacing: The distance between peaks reflects the frequency of contractions. More closely spaced peaks indicate contractions are occurring more frequently, which typically happens as labor progresses.

Contractions may start off mild and irregular in early labor, with lower peaks and longer intervals between them. As labor intensifies, the contractions become more regular, stronger, and closer together, producing taller and more frequent peaks.

How to Read a TOCO Monitor

Understanding how to read a TOCO monitor can help healthcare providers assess labor progression and make timely decisions about interventions if necessary. The key to interpreting TOCO readings is focusing on two main factors: the contraction number and the baseline uterine activity [*].

The TOCO number, displayed on the monitor, indicates the strength of each contraction. This number is measured in arbitrary units (AU) and can vary widely between individuals. Typically, the TOCO number increases as labor progresses and contractions become more intense [*].

• TOCO Number of 20-30: This range indicates mild contractions. These are often Braxton Hicks contractions, also known as "false labor" contractions, which are irregular and typically painless. Early labor contractions may also fall into this range.
• TOCO Number of 30-50: This range reflects moderate contractions, which are common during active labor. These contractions are more regular and help to dilate the cervix.
• TOCO Number of 50+: Contractions in this range are considered strong and are usually seen in the later stages of labor when the cervix is nearing full dilation and the baby is moving into the birth canal.

While the TOCO number provides an indication of contraction strength, it is important to remember that it is only one piece of the puzzle. Clinicians will also consider other factors, such as the mother's pain level, cervical dilation, and the baby’s heart rate when making decisions about labor management.

In addition to measuring contractions, the TOCO monitor tracks baseline uterine tone, which refers to the level of tension in the uterus between contractions. This is displayed as a flat or low-level line between contraction peaks on the monitor. A healthy labor typically involves a return to baseline activity between contractions, allowing the uterus to rest [*].

If the baseline uterine activity is elevated, it could be a sign of uterine irritability or hyperstimulation, conditions that may require medical intervention to prevent complications [*].

Contraction Monitor FAQ

What is a high contraction number on a TOCO monitor?

A high contraction number on a TOCO monitor is generally 50 or above. These numbers indicate strong, effective contractions that are helping to dilate the cervix and move labor forward. However, the interpretation of a “high” number can vary depending on individual circumstances and labor progression [*].

How does a tocodynamometer measure pressure?

A tocodynamometer measures pressure by detecting the tension exerted on the abdominal wall during uterine contractions. This pressure is converted into a numerical value, which reflects the strength of the contraction. It is a non-invasive method that gives healthcare providers a general sense of contraction intensity [*].

How accurate is the tocodynamometer?

While TOCO monitors provide useful data, they may not always give a completely accurate picture of contraction strength, particularly if the monitor is not positioned correctly or if the patient has a high body mass index (BMI). For more precise measurements, an intrauterine pressure catheter (IUPC) may be used, though this method is invasive and not used as frequently [*].

Where is the best place to place a TOCO monitor?

The ideal placement for a TOCO monitor is over the uterine fundus, the top portion of the uterus where contractions are strongest. This area is most sensitive to the pressure changes caused by uterine contractions, ensuring the monitor captures accurate readings [*].

Does TOCO pick up baby movement?

Yes, TOCO monitors can sometimes pick up baby movements, which may appear as irregularities or small spikes on the graph. However, these movements are usually distinguishable from contractions by their shape and timing. Trained professionals can differentiate between uterine contractions and fetal movement based on the monitor’s output [*].

The Bottom Line

TOCO monitors are a critical tool in labor and delivery, providing real-time data on uterine contractions.

By measuring contraction frequency, intensity, and duration, TOCO monitors help healthcare providers assess the progress of labor and make informed decisions about medical interventions.

For expectant mothers, understanding how to read TOCO monitor numbers can offer reassurance and a clearer picture of how labor is progressing.

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