title: Reference range of uterine artery Doppler parameters between the 11th and 14th pregnancy weeks in a population sample from Northeast Brazil.
abstract: OBJECTIVE
  To establish reference values for the first trimester uterine artery resistance index (UtA-RI) and pulsatility index (UtA-PI) in healthy singleton pregnant women from Northeast Brazil.
  
  
  METHODS
  A prospective observational cohort study including 409 consecutive singleton pregnancies undergoing routine early ultrasound screening at 11 - 14 weeks of gestation was performed. The patients responded to a questionnaire to assess maternal epidemiological characteristics. The left and right UtA-PI and UtA-RI were examined by color and pulsed Doppler by transabdominal technique and the mean UtA-PI, mean UtA-RI and the presence of bilateral protodiastolic notching were recorded. Quartile regression was used to estimate reference values.
  
  
  RESULTS
  The mean ± standard deviation UtA-RI and UtA-PI were 0.7 ± 0.1 and 1.5 ± 0.5, respectively. When segregated for gestation age, mean UtA-PI was 1.6 ± 0.5 at 11 weeks, 1.5 ± 0.6 at 12 weeks, 1.4 ± 0.4 at 13 weeks and 1.3 ± 0.4 at 14 weeks' gestation and mean UtA-RI was 0.7 ± 0.1 at 11 weeks, 0.7 ± 0.1 at 12 weeks, 0.6 ± 0.1 at 13 weeks and 0.6 ± 0.1 at 14 weeks' gestation. Uterine artery bilateral notch was present in 261 (63.8%) patients. We observed that the 5th and 95th percentiles of the UtA-PI and UtA-RI uterine arteries were 0.7 and 2.3 and, 0.5 and 0.8, respectively.
  
  
  CONCLUSIONS
  Normal reference range of uterine artery Doppler in healthy singleton pregnancies from Northeast Brazil was established. The 95th percentile of UtA-PI and UtA-RI values may serve as a cut-off for future prediction of pregnancy complications studies (i.e., pre-eclampsia) in Northeast Brazil.
authors.forename: Júlio Augusto Gurgel
authors.initials: JA
authors.lastname: Alves
authors.forename: Bruna Yang da Costa
authors.initials: BY
authors.lastname: Silva
authors.forename: Paulo Cesar Praciano
authors.initials: PC
authors.lastname: de Sousa
authors.forename: Sammya Bezerra
authors.initials: SB
authors.lastname: Maia
authors.forename: Fabrício da Silva
authors.initials: Fda S
authors.lastname: Costa
mesh_terms: D000328:Adult; D001938:Brazil; D005260:Female; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011446:Prospective Studies; D012016:Reference Values; D018608:Ultrasonography, Doppler; D018084:Ultrasonography, Interventional; D055988:Uterine Artery / Q000000981:diagnostic imaging* / Q000502:physiology*