title: Reference ranges for uterine artery mean pulsatility index at 11-41 weeks of gestation.
abstract: OBJECTIVE
  To construct gestational age (GA)-based reference ranges for the uterine artery (UtA) mean pulsatility index (PI) at 11-41 weeks of pregnancy.
  
  
  METHODS
  A prospective cross-sectional observational study was carried out of 20 consecutive singleton pregnancies for each completed gestational week at 11-41 weeks. UtAs were examined by color and pulsed Doppler imaging, and the mean PI, as well as the presence or absence of a bilateral protodiastolic notch, were recorded. Polynomials were fitted by means of least-square regression to estimate the relationship between the mean UtA-PI and GA.
  
  
  RESULTS
  A total of 620 women were included. A second-degree polynomial (Log(e) mean UtA-PI = 1.39 - 0.012 x GA + GA(2) x 0.0000198, with GA measured in days), after a natural logarithmic transformation, was selected to model our data. There was a significant decrease in the mean UtA-PI between 11 weeks (mean PI, 1.79; 95(th) centile, 2.70) and 34 weeks (mean PI, 0.70; 95(th) centile, 0.99). It then became more stable up until 41 weeks (mean PI, 0.65; 95(th) centile, 0.89).
  
  
  CONCLUSIONS
  The mean UtA-PI shows a progressive decrease until the late stages of pregnancy. Reference ranges for mean UtA-PI may have clinical value in screening for placenta-associated diseases in the early stages of pregnancy, and in evaluating patients with pregnancy-induced hypertension and/or small-for-gestational age fetuses during the third trimester.
authors.affiliation: Department of Maternal-Fetal Medicine, ICGON, Hospital Clínic, University of Barcelona and Center for Biomedical Research on Rare Diseases (CIBERER), Barcelona, Spain. ogomez@clinic.ub.es
authors.forename: O
authors.initials: O
authors.lastname: Gómez
authors.forename: F
authors.initials: F
authors.lastname: Figueras
authors.forename: S
authors.initials: S
authors.lastname: Fernández
authors.forename: M
authors.initials: M
authors.lastname: Bennasar
authors.forename: J M
authors.initials: JM
authors.lastname: Martínez
authors.forename: B
authors.initials: B
authors.lastname: Puerto
authors.forename: E
authors.initials: E
authors.lastname: Gratacós
mesh_terms: D000328:Adult; D001158:Arteries / Q000000981:diagnostic imaging; D004812:Epidemiologic Methods; D005260:Female; D005317:Fetal Growth Retardation / Q000000981:diagnostic imaging; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D011225:Pre-Eclampsia / Q000000981:diagnostic imaging; D011247:Pregnancy; D011673:Pulsatile Flow / Q000502:physiology; D012016:Reference Values; D018617:Ultrasonography, Doppler, Pulsed / Q000379:methods*; D016216:Ultrasonography, Prenatal / Q000379:methods*; D014469:Umbilical Arteries / Q000000981:diagnostic imaging / Q000503:physiopathology; D014599:Uterus / Q000098:blood supply*