title: Uteroplacental Doppler flow velocity waveform indices in normal pregnancy: a statistical exercise and the development of appropriate reference values.
abstract: In a prospective cross-sectional study, we examined 154 normal pregnant women and measured the systolic to diastolic (S/D) ratio and resistance index (RI) in the umbilical artery and both uterine arteries. Placental location with respect to laterality was determined by real-time ultrasound. In patients with unilateral placental location, each uterine artery was evaluated according to its relationship with the placenta. Doppler flow velocity waveforms were obtained by a continuous wave Doppler device. Kolmogorov D tests revealed that RI values follow gaussian distribution, but that S/D values were markedly skewed to the right. There was a significant negative linear relationship between gestational age and umbilical artery RI and a significant negative curvilinear relationship between gestational age and umbilical artery (S/D (r = 0.83, p less than 0.001; and r = -0.79, p less than 0.001, respectively). Confidence bands for umbilical artery RI were developed based on the linear model with gestational age (fitted umbilical artery RI = 0.97199 - 0.01045*gestational age). Confidence bands for umbilical artery S/D were derived from the corresponding RI values by means of the functional relationship S/D = 1/(1 - RI). The RI and S/D values of the uterine arteries declined until 24 to 25 weeks' gestation and remained unchanged thereafter. This relationship, however, was not statistically significant (r = -0.10, p = 0.22). The placental uterine artery is different from the nonplacental quantitatively and qualitatively.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Obstetrics and Gynecology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, North Carolina.
authors.forename: A D
authors.initials: AD
authors.lastname: Kofinas
authors.forename: M A
authors.initials: MA
authors.lastname: Espeland
authors.forename: M
authors.initials: M
authors.lastname: Penry
authors.forename: M
authors.initials: M
authors.lastname: Swain
authors.forename: C G
authors.initials: CG
authors.lastname: Hatjis
mesh_terms: D003430:Cross-Sectional Studies; D003971:Diastole; D005260:Female; D005865:Gestational Age; D006801:Humans; D010920:Placenta / Q000098:blood supply* / Q000000981:diagnostic imaging; D011247:Pregnancy / Q000502:physiology*; D011446:Prospective Studies; D012016:Reference Values; D012044:Regression Analysis; D013599:Systole; D016216:Ultrasonography, Prenatal; D014469:Umbilical Arteries / Q000000981:diagnostic imaging / Q000502:physiology*; D014599:Uterus / Q000098:blood supply* / Q000000981:diagnostic imaging; D014655:Vascular Resistance