Four-channel tocography in uneventful pregnancies: a prospective study in primigravidas and multigravidas

The simultaneous recording of external uterine pressure in four locations on the abdominal wall with four-channel-tocography provides new ways to describe the dynamics of uterine activity.

Fifty-eight healthy primigravidas and 25 healthy multigravidas were studied prospectively with four-channel tocography during the course of pregnancy. Starting at 21 weeks' gestation, the following five intervals were defined: 21-24, 25-28, 29-32, 33-36 and more than 37 completed weeks. Eligibility criteria included informed consent, no history of malformations of the uterus, and no previous preterm deliveries. Patients were excluded for the following reasons: medication for preterm labor, cerclage, placenta previa, delivery before 37 weeks' gestation, less than three measurements completed, and patient's withdrawal of consent.

The median contraction frequency per hour was six for primigravidas and five for multigravidas, without significant correlation with gestational age. At all time periods studied, the median rate of global contractions developing simultaneously in at least three uterine segments was less than 15%; however, it was significantly higher in primigravidas than in multigravidas (14% versus 4%, P <.001). Both groups had more activity in the right upper quadrant of the uterus shortly before delivery.

Four-channel tocography provided insight into uterine activity patterns and might enable obstetricians to select clinically relevant contractions for further treatment.