title: Placental site does not change background uterine electromyographic activity in the middle trimester of pregnancy.
abstract: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  Background uterine EMG activity measured from the abdominal surface in the middle trimester of pregnancy does not depend on the placental implantation site.
authors.affiliation: University Department of Obstetrics and Gynecology, School of Medicine, Zagreb University, Sveti Duh Hospital, Sveti Duh 64, 10000 Zagreb, Croatia. ozreng@net.hr
authors.forename: Ozren
authors.initials: O
authors.lastname: Grgic
authors.forename: Ratko
authors.initials: R
authors.lastname: Matijevic
authors.forename: Oliver
authors.initials: O
authors.lastname: Vasilj
mesh_terms: D000200:Action Potentials; D000328:Adult; D015331:Cohort Studies; D004576:Electromyography / Q000379:methods* / Q000592:standards; D010064:Embryo Implantation / Q000502:physiology*; D005260:Female; D006801:Humans; D010920:Placenta / Q000502:physiology*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011446:Prospective Studies; D012815:Signal Processing, Computer-Assisted; D018709:Statistics, Nonparametric; D014590:Uterine Contraction / Q000502:physiology*; D014599:Uterus / Q000502:physiology