ABSTRACT
The use of home uterine activity monitoring for patients at high risk for preterm
labor and delivery has become common in clinical perinatology. The ability of the
monitoring devices to detect accurately uterine contractions in early pregnancy has
not previously been reported. Ten women in labor between 20 and 35 weeks' gestation
underwent simultaneous monitoring of uterine activity with a guard-ring tocodynamometer
and an intrauterine pressure monitor. When compared with internal monitoring, the
external monitor detected 90.8% of uterine contractions with a specificity for uterine
quiescence of 98.1% The predictive value of external monitoring was 97.3% for detecting
uterine contractions and 93.6% for recording the absence of uterine contractions.
The contractions detected externally were similar in duration: mean 63.7 ± 23.0 seconds
for internal monitoring and 62.2 ± 22.6 seconds for external monitoring (p >0.05).
The intensity of contractions detected externally was less than internally measured
contractions, mean difference, 19.7 ± 15.9 mmHg (p <0.001). External tocodynamometry
using this guard-ring tocodynamometer reliably distinguishes between uterine contractions
and uterine quiescence in preterm pregnancies but does not adequately measure the
intensity of contractions.
