Tocometry (TOCO) monitors uterine contractions during pregnancy and labor. This non-invasive technique assesses the well-being of both the pregnant individual and the fetus. It provides insights into uterine activity, helping healthcare providers understand labor progression and identify concerns.
Understanding Tocometry
TOCO measures the frequency and duration of uterine contractions. It indicates a relative change in pressure as the uterus tightens, not precise intensity. Monitoring uterine activity tracks labor progression, evaluates for preterm labor, and assesses intervention effectiveness. This is typically performed alongside fetal heart rate monitoring for a comprehensive view of fetal response.
How TOCO Readings Are Taken
External TOCO readings use a tocodynamometer, a pressure-sensitive disc placed on the maternal abdomen, usually over the uterus. This device detects abdominal pressure changes from contractions and transmits data to a monitor. While non-invasive, its accuracy is influenced by the pregnant person’s position, body size, and proper monitor placement. For direct intensity measurement, an intrauterine pressure catheter (IUPC) may be used. An IUPC is an invasive device inserted into the uterus after amniotic sac rupture, providing quantitative pressure readings in mmHg.
Interpreting Normal TOCO Ranges
Interpreting TOCO readings involves understanding normal uterine activity at different stages. For individuals not in active labor or experiencing early labor, such as Braxton Hicks contractions, TOCO readings show infrequent, mild, and irregular activity. These typically register 5-25 mmHg. Braxton Hicks contractions do not increase in intensity or frequency over time and do not cause cervical changes.
As active labor progresses, contractions become more frequent, longer, and regular. A typical pattern shows contractions every 2-5 minutes, lasting 30-70 seconds. External tocometer readings during active labor can range from 40 to 70 mmHg. During the second stage, contractions are strongest and most frequent, potentially reaching 50-100 mmHg.
Normal uterine activity includes a healthy resting tone between contractions, where the uterus relaxes completely. This allows blood flow to the placenta and ensures fetal oxygenation. On an external TOCO tracing, this is indicated by the tracing returning to baseline. For internal IUPC monitoring, the normal resting tone is 8-12 mmHg. Normal ranges vary among individuals and labor stages, requiring clinical context for proper interpretation.
When TOCO Readings Are Not Normal
Deviations from normal TOCO patterns require medical attention. Uterine tachysystole (hyperstimulation) is defined as more than five contractions in a 10-minute period, averaged over 30 minutes. It can also involve single contractions lasting two minutes or more, or contractions occurring within one minute of each other.
Tachysystole can compromise uteroplacental blood flow, leading to fetal hypoxia, because excessive contractions reduce relaxation time. Another concerning pattern is ineffective contractions, which are too infrequent, short, or weak to facilitate cervical changes.
Healthcare providers correlate TOCO readings with fetal heart rate patterns, as abnormal uterine activity can cause fetal heart rate changes like decelerations. Abnormal readings prompt further assessment and interventions for the well-being of both the pregnant individual and the fetus.