title: Uterine artery Doppler measurements during first and second trimesters of normal pregnancy.
abstract: BACKGROUND
  The aim of this study was to construct a reference curve based on longitudinal Doppler blood flow measurements of the uterine artery during the first and second trimesters of normal pregnancy.
  
  
  METHODS
  Healthy pregnant women (n = 124) between 18 and 38 years of age were included. The uterine artery pulsatility index (UtAPI) was measured with transvaginal ultrasound in the first trimester (gestational weeks 8-10 and 11-13) and with transabdominal ultrasound in the second trimester (gestational weeks 18 and 24). Individual longitudinal curves were constructed and a reference curve was created.
  
  
  RESULTS
  A centile curve with the normal distribution of the UtAPI during the first and second trimesters was constructed. We found that 90% of the women alternated between quartiles during the four examinations between gestational weeks 8 and 24, but 75% remained within the higher or lower range.
  
  
  CONCLUSIONS
  A UtAPI reference curve was constructed for the first and second trimesters of pregnancy. Although the mean UtAPI values may vary from one examination to the next, most mean UtAPI values remain within the higher or lower range, i.e. above or below the 50th centile.
authors.affiliation: National Center for Fetal Medicine, St. Olav's Hospital, Trondheim University Hospital, Trondheim, Norway.|Department for Laboratory Medicine, Children's and Women's Health, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Solhild
authors.identifier: http://orcid.org/0000-0001-6146-435X
authors.initials: S
authors.lastname: Stridsklev
authors.affiliation: Unit for Applied Clinical Research, Department for Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Salvesen
authors.affiliation: Department for Laboratory Medicine, Children's and Women's Health, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Kjell Å
authors.initials: KÅ
authors.lastname: Salvesen
authors.affiliation: Unit for Applied Clinical Research, Department for Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway.|Department of Endocrinology, St. Olav's Hospital, Trondheim University Hospital, Trondheim, Norway.
authors.forename: Sven M
authors.initials: SM
authors.lastname: Carlsen
authors.affiliation: Department for Laboratory Medicine, Children's and Women's Health, Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: May A
authors.initials: MA
authors.lastname: Husøy
authors.affiliation: Department for Laboratory Medicine, Children's and Women's Health, Norwegian University of Science and Technology, Trondheim, Norway.|Department of Obstetrics and Gynecology, St. Olav's Hospital, Trondheim University Hospital, Trondheim, Norway.
authors.forename: Eszter
authors.identifier: http://orcid.org/0000-0002-5741-076X
authors.initials: E
authors.lastname: Vanky
mesh_terms: D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity; D005260:Female; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000502:physiology*; D011262:Pregnancy Trimester, Second / Q000502:physiology*; D011673:Pulsatile Flow; D012016:Reference Values; D018608:Ultrasonography, Doppler; D055988:Uterine Artery / Q000502:physiology*; D014599:Uterus / Q000098:blood supply*; D055815:Young Adult
keywords: Polycystic ovary syndrome; pregnancy; pulsatility index; ultrasound; uterine artery