External four channel tocography in preterm labor. First results.

In order to known more about preterm labor the objective of our investigation was to look for a correlation between the spatial and temporal pattern of uterine contractions and the duration of pregnancy. 50 patients with preterm labor between 21 and 35 weeks of gestation underwent repeated measurements using four-channel tocography in which the pressure of contractions was registered simultaneously on the left and right sides at the fundus and the lower segment of the uterus. Half of all recorded signals were locally restricted (typical labor pattern in only one or two registration tracks). The following two phenomena were significantly associated with a shorter duration of pregnancy: 1. the reproducibility of a center of dominance (defined as the locus of registration with the highest sum of amplitudes), and 2. a predominant origin of labor in the right fundal region of the uterus. Four-channel tocography indicates whether preterm labor is likely to lead to preterm delivery. It may therefore help the obstetrician in deciding whether to use tocolytic therapy.