TOCO is short for tocodynamometer, a device that is used to measure the duration, frequency and relative strength of uterine contractions in pregnant women, according to the Center for Experiential Learning. TOCO devices are noninvasive. They are pressure-sensitive devices that are held against the abdomen of a pregnant woman by a belt or band and respond to and record changes in uterine muscles, according to Johns Hopkins Medicine.
Because contractions can affect fetal heart rate, a TOCO device is often used together with a fetal heart rate monitor, according to Johns Hopkins. A Doppler ultrasound device is strapped to the woman's abdomen to detect fetal heart rate, usually by the same band as the TOCO device. The TOCO device is situated under the band or belt just below the top of the fundus, according to Austin Community College, while the ultrasound device is placed over the site of strongest fetal heartbeat and may need to be moved as the fetus moves. The results of the two devices are either displayed on a computer monitor or printed on paper, where they can be compared so that fetal heart beat during and between contractions can be determined. According to Obstetrics & Gynecology, TOCO devices are not always accurate, especially when used on obese women.