The human study begins immediately after placing the catheter and lasts 60 minutes; FHR, uterine contraction timing, and subjective contraction amplitude are monitored during the entire study. The first 20 minutes are the control contraction period (C1). The second 20 minutes are the EI period, with a 10-second burst of current administered just prior to each expected contraction; expected contractions are determined by the timing of the C1 contractions and/or by the rise of the subjective tocodynamometer tracing above baseline levels. The third 20 minutes is the post-intervention control contraction period (C2). The contraction intervals, the times between contraction peaks (P-P), were measured in minutes for C1, EI, and C2. All statistical analyses for the human study have been performed using Statistical Analysis System (SAS) software (SAS Institute Inc., Cary, NC, USA) Version 9.2. For each period, C1, E1, and C2, the mean minutes between contractions are estimated, using the mixed-model analysis of variance (ANOVA) to account for both within-subject and between-subject variability. Pairwise differences between mixed-model ANOVA means and corresponding p-values testing for difference from zero were estimated. All hypothesis testing is performed at the 0.05 level of significance.