title: Reference values for blood flow velocity in the uterine artery in normal pregnancies from 18 weeks to 42 weeks of gestation calculated by automatic Doppler waveform analysis.
abstract: OBJECTIVE
  The goal of the present study was to establish new Doppler reference ranges for maternal heart rate, intensity-weighted mean blood flow velocities (Vmean) and impedance indices (PI, RI) for the uterine artery by automated waveform analysis.
  
  
  METHODS
  A cross-sectional prospective study of 921 low-risk pregnancies was performed at 18 - 42 weeks of gestation. Uterine blood flow velocities were derived with pulsed-wave color Doppler. Measurements were carried out 1 to 2 cm above the crossing of the uterine and external iliac arteries. Reference ranges for the individual measuring parameters were constructed based on a growth function from a four-parameter class of monotonic continuous functions according to the smallest square principle.
  
  
  RESULTS
  A significant increase in intensity-weighted mean uterine blood flow velocities was observed at 18 - 42 weeks of gestation (Vmean = 43 cm/s to 50 cm/s (p < 0.001)). Reference curves for the pulsatility and resistance indices (PI, RI) significantly decreased with progressing gestation (PI: 18 weeks: 0.89; 42 weeks: 0.65 and RI: 18 weeks: 0.45; 42 weeks: 0.35). No significant PI and RI differences were observed when different placental locations were compared. The maternal heart rate decreased from 88 bpm to 77 bpm.
  
  
  CONCLUSIONS
  Normal ranges for blood flow velocities and impedance indices in the uterine artery were established by Doppler ultrasound antenatal examinations of a large population of low-risk pregnancies. The data are proposed as reference curves to allow the early diagnosis of maternal and fetal risks.
authors.affiliation: Obstetrics and Gynecology, Bürgerhospital, Frankfurt. f.bahlmann@buergerhospitalffm.de
authors.forename: F
authors.initials: F
authors.lastname: Bahlmann
authors.forename: M
authors.initials: M
authors.lastname: Fittschen
authors.forename: I
authors.initials: I
authors.lastname: Reinhard
authors.forename: S
authors.initials: S
authors.lastname: Wellek
authors.forename: E
authors.initials: E
authors.lastname: Steiner
mesh_terms: D001783:Blood Flow Velocity / Q000502:physiology*; D003430:Cross-Sectional Studies; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007231:Infant, Newborn; D011247:Pregnancy; D011262:Pregnancy Trimester, Second / Q000502:physiology*; D011263:Pregnancy Trimester, Third / Q000502:physiology*; D011446:Prospective Studies; D011673:Pulsatile Flow / Q000502:physiology; D012016:Reference Values; D012044:Regression Analysis; D018615:Ultrasonography, Doppler, Color / Q000379:methods*; D018617:Ultrasonography, Doppler, Pulsed / Q000379:methods*; D055988:Uterine Artery / Q000000981:diagnostic imaging* / Q000502:physiology*