title: Correlation between the Doppler velocimetry findings of the uterine arteries during the first and second trimesters of pregnancy.
abstract: OBJECTIVE
  Evaluate the feasibility of transvaginal uterine artery Doppler examination in the first and second trimesters of pregnancy, establish reference ranges in a Brazilian population and examine the correlation between these Doppler findings.
  
  
  METHODS
  Longitudinal prospective study at the antenatal clinic of a tertiary teaching hospital. Uterine artery Doppler examinations were carried out transvaginally at 11 to 14 weeks and 20 to 25 weeks of gestation. Uterine artery mean pulsatility index (PI) distributions were determined and the presence or absence of an early diastolic notch was also noted. The degree of correlation between first and second trimester Doppler findings was examined.
  
  
  RESULTS
  Three hundred and forty four women with live singleton pregnancies and normal outcome were first examined at a mean gestation of 12.7 weeks. The values corresponding to the 50th and 95th centiles of mean PI were 1.69 and 2.48. Bilateral notches were observed in 44% of cases and unilateral notches were present in 19%. Second trimester Doppler examinations were carried out at a mean gestation of 23.2 weeks and corresponding figures for the 50th and 95th centiles were 1.03 and 1.57. Bilateral notches were noted in 4.4% of the cases. First trimester impedance indices were significantly higher and positively correlated to second trimester findings (r = 0.42, p<0.0001).
  
  
  CONCLUSIONS
  Uterine artery Doppler examination can be successfully performed transvaginally and incorporated into scans that are routinely offered to women during their antenatal care in the first and second trimesters. Doppler indices obtained during the first trimester are significantly higher than those of the second trimester and findings at both scans are significantly correlated.
authors.affiliation: setor de medicina fetal, Clínica Obstétrica do Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo.
authors.forename: Adolfo Wenjaw
authors.initials: AW
authors.lastname: Liao
authors.forename: Julio
authors.initials: J
authors.lastname: Toyama
authors.forename: Verbênia
authors.initials: V
authors.lastname: Costa
authors.forename: Carla
authors.initials: C
authors.lastname: Ramos
authors.forename: Maria
authors.initials: M
authors.lastname: Brizot
authors.forename: Marcelo
authors.initials: M
authors.lastname: Zugaib
mesh_terms: D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000502:physiology; D011262:Pregnancy Trimester, Second / Q000502:physiology; D011446:Prospective Studies; D012016:Reference Values; D012039:Regional Blood Flow / Q000502:physiology; D018617:Ultrasonography, Doppler, Pulsed / Q000379:methods*; D055988:Uterine Artery / Q000000981:diagnostic imaging* / Q000502:physiology