Qualitative evaluation of uterine contractions recorded by a double guard-ring tocodynamometer

Qualitative characteristics of uterine contractions in various labors were evaluated by a double guard-ring tocodynamometer, according to the percentages of concurrent and synchronous contractions of two contraction curves when compared with overall contractile activity. For term and preterm labors, percentages of both concurrent and synchronous contractions were significantly higher than those of Braxton Hicks contractions; however, the concurrent and synchronous percentages of preterm labor were lower than those of term labor. Synchronous percentage in groups under maintenance therapy or active treatment in preterm labor were nearly the same; however, the percent concurrent under maintenance therapy was significantly lower than that during active treatment. Both concurrent and synchronous percentages were significantly higher during the active phase of labor than those during the latent phase. The percentages in the latent and active phases of spontaneous contractions were nearly the same; however, they increased significantly during the active phase of augmented contractions, as compared with the latent phase. When the percentages of concurrent and synchronous contractions at each cervical dilatation were retrospectively examined, both values increased significantly between 5 and 6 cm of cervical dilatation. The results suggest that this method can provide important information for understanding the quality of the contraction if attention is paid to the percentages of concurrent and synchronous contractions of two contraction curves and will aid in determining whether oxytocin or tocolysis should be given in term or preterm labor.