title: Effect of uterine contractions on fetal heart rate in pregnancy: a prospective observational study.
abstract: BACKGROUND
  The new Holter monitoring technology enables long-term electrocardiographic recording of the fetal heart rate without discomfort for the mother. The aim of the study was to assess the feasibility of a fetal Holter monitor. This technology was further used to study fetal heart rate outside the hospital setting during normal daily activities and to test the hypothesis that uterine activity during pregnancy influences fetal heart rate.
  
  
  METHODS
  Prospective observational study including 12 healthy pregnant women at 20-40 weeks of gestation. Data were collected using the Monica AN24 system. Outcome measures were fetal heart rate, maternal heart rate, and uterine activity categorized according to the strength of the electrohysterographic signal.
  
  
  RESULTS
  The recordings had a median length of 18.8 h, and fetal heart rate and maternal heart rate were obtained with success rates of 73.1 and 99.9%, respectively. Uterine activity was found to affect fetal heart rate in all participants. Compared with the basal tone and mild levels of uterine activity, moderate and strong levels of uterine activity were associated with increases in fetal heart rate of 4.0 and 5.7 beats/min, respectively. At night, the corresponding increases were 4.9 and 7.6 beats/min. Linear correlations were found between maternal heart rate and fetal heart rate in 11 of the 12 cases, with a mean coefficient beta of 0.189. Both maternal heart rate and fetal heart rate exhibited a diurnal pattern, with lower heart rates being recorded at night.
  
  
  CONCLUSIONS
  Uterine activity during pregnancy is associated with a graded response in fetal heart rate and may represent a physiological challenge for the development and adaptation of the fetal cardiovascular system.
authors.affiliation: Department of Clinical Science, University of Bergen, Bergen, Norway.
authors.forename: Julie
authors.initials: J
authors.lastname: Sletten
authors.affiliation: Department of Clinical Science, University of Bergen, Bergen, Norway.|Department of Obstetrics and Gynecology, Haukeland University Hospital, Bergen, Norway.
authors.forename: Torvid
authors.identifier: http://orcid.org/0000-0003-1825-1660
authors.initials: T
authors.lastname: Kiserud
authors.affiliation: Department of Clinical Science, University of Bergen, Bergen, Norway. jorg.kessler@kk.uib.no.|Department of Obstetrics and Gynecology, Haukeland University Hospital, Bergen, Norway. jorg.kessler@kk.uib.no.
authors.forename: Jörg
authors.identifier: http://orcid.org/0000-0003-2931-2668
authors.initials: J
authors.lastname: Kessler
mesh_terms: D000328:Adult; D015148:Cardiotocography; D005240:Feasibility Studies; D005260:Female; D005323:Fetal Monitoring / Q000379:methods*; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D011247:Pregnancy; D011256:Pregnancy Outcome; D011446:Prospective Studies; D012015:Reference Standards; D014590:Uterine Contraction / Q000502:physiology*; D055815:Young Adult
keywords: Fetal heart rate; electrohysterography; fetal Holter monitor; maternal heart rate; uterine contraction