Placental site does not change background uterine electromyographic activity in the middle trimester of pregnancy

OBJECTIVE: This study was performed in order to assess the potential influence of placental implantation site on transabdominal electromyographic (EMG) assessment of the uterine electrical activity in the middle trimester of pregnancy. STUDY DESIGN: In this prospective study 251 unselected, nulliparous asymptomatic women with a singleton pregnancy underwent transabdominal uterine EMG. Uterine electrical activity was recorded using bipolar electrodes placed on the abdominal surface for 20min. Regarding the placental implantation site and presence of action potentials (AP) pregnant women were divided into two groups: the anterior placenta group (APG) and the posterior placenta group (PPG). Outcome measures were differences in the median frequency (MF) and median amplitude (MA) of AP between the two groups. RESULTS: Action potentials were detected in 56 women: 33/56 in the APG versus 23/56 in the PPG. The parameters analyzed (MF, p=0.527, Fisher's exact test, and MA, p=0.255, Fisher's exact test) did not produce any statistical significant differences between the two groups. CONCLUSION: Background uterine EMG activity measured from the abdominal surface in the middle trimester of pregnancy does not depend on the placental implantation site.