Vaginal electrohysterography: the design and preliminary evaluation of a novel device for uterine contraction monitoring in an ovine model*

Abstract

Objective Tocodynamometry is the most common method of labor evaluation but most clinicians would agree it has limited utility before 26 weeks gestation. The obesity epidemic has further reduced our ability to accurately detect uterine contractions using the tocodynamometer at any gestational age. We sought to design and test a novel contraction monitor that bypasses the maternal abdomen. Methods An optimized version of an intravaginal electrohysterographic ring device was tested in an ovine model. The device and its methodology as well as the tocodynamometer were validated against the current gold standard uterine activity monitor, the intrauterine pressure catheter in 6 sheep at varying gestational ages. Results Both the intravaginal ring device and the tocodynamometer correlated well with IUPC, r = 0.69 and 0.73 respectively (p<0.001). The number of contractions detected by each monitor remained similar even after accounting for confounders. Conclusions These results suggest that uterine activity can be monitored from the vaginal interface in an ovine model and offers an alternative clinical tool for the detection of contractions in situations in which tocodynamometry would be ineffective or intrauterine monitoring inappropriate.