Uterine Contraction Assessment
Core concepts
Contractions are described by frequency, duration, intensity, and resting tone. Frequency is counted from the start of one contraction to the start of the next, usually over a 10-minute window. Duration is from onset to offset. Intensity is assessed by palpation or intrauterine catheter. Resting tone is the pressure between contractions and should be low.
Normal labor progresses with contractions that increase in frequency and intensity. Excessive uterine activity, sometimes called tachysystole, is more than five contractions in 10 minutes averaged over 30 minutes. It matters because it reduces placental perfusion between contractions. Causes include oxytocin, prostaglandins, and abruption.
Assessment also includes maternal response: pain, coping, and vital signs. Contraction patterns alone do not define adequacy of labor; cervical change matters.
Traps
Questions often test the counting window and the definition of tachysystole. Another trap is confusing frequency with duration, or assuming a strong contraction on palpation equals adequate labor progress. Also remember that resting tone elevation can indicate abruption or overstimulation.
Rule of thumb
Count contractions over 10 minutes, average over 30 minutes, and act when there are more than five in 10 minutes with a non-reassuring fetal heart rate.
Worked example
A patient on oxytocin has contractions every two minutes lasting 70 seconds with a baseline fetal heart rate of 150 and recurrent late decelerations. That is more than five contractions in 10 minutes. Reduce or stop oxytocin, reposition, and give fluids; notify the provider.