title: Uterine contractions increase fetal heart preload.
abstract: OBJECTIVE
  The preload index (PLI) has been shown to increase in the recipient fetus of twin-twin transfusion syndrome in the presence of uterine contractions. The objective of this study was to determine whether there are changes in PLI in the presence of uterine contractions in normal fetuses.
  
  
  METHODS
  Inferior vena cava blood flow was measured using Doppler sonography in 45 normal fetuses at 18-41 weeks' gestation in the presence of uterine contractions and during quiescence and the PLI was compared between groups.
  
  
  RESULTS
  There was a highly significant difference (P < 0.0001) between the mean +/- SD PLI in fetuses in the absence (0.235 +/- 0.07) and in the presence (0.534 +/- 0.183) of uterine contractions.
  
  
  CONCLUSIONS
  Uterine contractions appear to increase fetal preload conditions in normal pregnancy.
authors.affiliation: Department of Obstetrics and Gynecology, Gifu University School of Medicine, Gifu City, Japan. y-taka@cc.gifu-u.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Takahashi
authors.forename: S
authors.initials: S
authors.lastname: Iwagaki
authors.forename: Y
authors.initials: Y
authors.lastname: Nakagawa
authors.forename: I
authors.initials: I
authors.lastname: Kawabata
authors.forename: T
authors.initials: T
authors.lastname: Tamaya
mesh_terms: D001783:Blood Flow Velocity; D005260:Female; D005865:Gestational Age; D006340:Heart Rate, Fetal / Q000502:physiology*; D006801:Humans; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D018608:Ultrasonography, Doppler; D016216:Ultrasonography, Prenatal; D014590:Uterine Contraction / Q000502:physiology*; D014682:Vena Cava, Inferior / Q000502:physiology