Monitoring labor is an important aspect of childbirth, allowing healthcare providers to observe the progress of uterine contractions. This process often involves external devices that track uterine activity, providing valuable data without invasive procedures. Understanding how these contractions are measured offers insight into the information professionals use to support individuals during labor.
The Toco Device and Its Function
A tocodynamometer, commonly called a toco, is a non-invasive device used to monitor uterine contractions. This instrument consists of a flat, disk-shaped pressure transducer housed within a belt secured around the maternal abdomen. Healthcare providers position the toco over the fundus, the top part of the uterus, where contractions are most detectable. As the uterus contracts, it hardens and changes shape, exerting pressure against the transducer.
The toco device works by converting this mechanical pressure into an electrical signal. This signal is then transmitted to a fetal monitor, which displays the data visually. The primary function of the toco is to measure the frequency and duration of uterine contractions, providing a continuous recording of uterine activity.
Understanding Contraction Readings
When people refer to a “toco number,” they are generally not speaking of a single, fixed numerical value. Instead, the term refers to the patterns and data points derived from toco monitoring, displayed as a graphical representation resembling hills or bell-shaped curves. These readings are typically measured in millimeters of mercury (mmHg). The baseline reading, when the uterus is at rest between contractions, is usually around 10 to 12 mmHg.
The key aspects observed from toco readings are the frequency and duration of contractions. Frequency is determined by timing the interval from the beginning of one contraction to the beginning of the next. Duration measures how long each individual contraction lasts, from its start to its end.
For instance, contractions in active labor might be recorded as occurring every three to five minutes and lasting between 40 to 70 seconds. Braxton Hicks contractions, often known as “false labor,” typically show lower readings (5-25 mmHg), while active labor contractions may range from 40-70 mmHg, and can reach 50-100 mmHg during the pushing stage.
Why Toco Monitoring is Used
Toco monitoring assesses labor progress. By observing contraction frequency and duration, healthcare providers gain insights into labor advancement. This information helps evaluate contraction effectiveness in moving labor forward. Continuous uterine activity monitoring also helps correlate contraction patterns with the baby’s heart rate, a process known as cardiotocography.
This combined assessment monitors the well-being of both the birthing individual and the baby throughout labor. It allows medical teams to identify potential issues, such as overly frequent or prolonged contractions, which could affect fetal oxygenation. Data from toco monitoring supports timely clinical decisions, especially when labor is induced or augmented with medications like oxytocin.
What Toco Monitoring Doesn’t Show
External toco monitoring has specific limitations. It does not accurately measure the true intensity or strength of uterine contractions. The device senses tension or pressure on the abdominal wall, which is a relative measure, rather than the actual pressure inside the uterus. This means that a higher “toco number” indicates greater external pressure, but it does not directly correlate to the internal force of the contraction.
External factors can influence toco readings, including patient movement, transducer placement, and body habitus. For example, changes in position or a higher body mass index can affect reading accuracy and consistency. To obtain a precise measurement of contraction intensity, an internal monitoring method, such as an intrauterine pressure catheter (IUPC), is necessary. However, internal monitoring requires ruptured membranes and carries its own considerations.