Uterine Contractions in Normal Labor Developed by a Positive Feed-back and Oscillation

Regular uterine contractions in normal labor are expulsive power to deliver the fetus. The intrauterine pressure changes were recorded and studied in the measurement of labor contractions of uterus, while external tocodynamometry is common in clinical fetal monitoring [1]. The duration of contraction was about 1 min and interval was also 1 min, and the peak intrauterine pressure was 30 to 50 mmHg in normal labor contractions, which was initiated at the pace-maker located at the corner of uterine fundus [1], it was conducted by the gap-junction [2] from the fundus to the cervix [1]. In addition, myometrial action potential was studied in details [3-5]. However, no mechanism of regular uterine contractions has been clarified, though the regular and constant myometrial contraction intensity would be important feature to push the fetus downwards and dilate the cervix. First step of studies was the detection of regular contraction, second the simulation of the repeated contraction comparing to electric oscillation in this report.