Electrical Activity of the Human Uterus in Labor

¹ From the Department of Obstetrics and Gynecology, and the Department of Biophysics, School of Medicine, University of California at Los Angeles, Los Angeles, California

Electrical activities of the pregnant uterus in labor were studied in 130 women, providing a total of 736 uterine contraction cycles. It was shown that there existed a spike and slow wave pattern in early to middle first stage of labor whose period was that of the uterine contraction. Mean amplitudes were 2.45 millivolts for the spike, 3.68 mv for the diphasic swing, and 6.74 mv for the slow wave. Mean durations were: U_a–U_b interval 29.83 seconds, U_b–U_c interval 35.08 seconds and U_a–U_c interval 68.10 seconds. These time values were significantly decreased in the last third of first stage labor and in the second stage. It was emphasized that there was a great deal of variability, both in the same patient as labor progressed and in the records from patient to patient.