title: Middle cerebral artery peak systolic velocity in monochorionic and dichorionic twin pregnancies.
abstract: OBJECTIVE
  The purpose of this study was to compare middle cerebral artery (MCA) peak systolic velocity (PSV) values in monochorionic (MC) and dichorionic (DC) twin pregnancies.
  
  
  METHODS
  This was a prospective cohort study in which MCA Doppler evaluation was performed in unselected twin pregnancies at time of routine sonography between 28 and 32 weeks. Pregnancies with known fetal anomalies, twin-twin transfusion syndrome, and red cell alloimmunization or other conditions associated with anemia were excluded. The intertwin MCA PSV difference, defined as the larger minus smaller PSV value within a pair, was compared in MC and DC pregnancies and was correlated with estimated fetal weight and birth weight discordance. Statistical analyses included Spearman correlation, analysis of variance, a t test, and a chi(2) test.
  
  
  RESULTS
  Doppler indices were analyzed from 48 twin pregnancies, of which 32 (67%) were DC and 16 (33%) were MC. There was no difference in proportion of values above or below the singleton median for either the larger or smaller DC or MC twins (all P > or = .3). The median intertwin MCA PSV difference was 4.9 cm/s in MC pregnancies and 4.5 cm/s in DC pregnancies (P = .6). There was no significant correlation between the MCA PSV difference and either estimated fetal weight discordance or birth weight discordance in either MC or DC pregnancies (all P > or = .3).
  
  
  CONCLUSIONS
  Middle cerebral artery PSV values in uncomplicated twin pregnancies are comparable with published singleton norms, with a median intertwin MCA PSV difference of approximately 5 cm/s. We found no significant correlation between the intertwin MCA PSV difference and discordance in MC or DC twin gestations.
authors.affiliation: Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd, Dallas, TX 75390-9032 USA. jodi.dashe@utsouthwestern.edu
authors.forename: Jodi S
authors.initials: JS
authors.lastname: Dashe
authors.forename: Ronald M
authors.initials: RM
authors.lastname: Ramus
authors.forename: Rigoberto
authors.initials: R
authors.lastname: Santos-Ramos
authors.forename: Donald D
authors.initials: DD
authors.lastname: McIntire
authors.forename: Diane M
authors.initials: DM
authors.lastname: Twickler
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D005260:Female; D006801:Humans; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging* / Q000502:physiology*; D011247:Pregnancy; D011379:Prognosis; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014427:Twins / Q000502:physiology*; D016216:Ultrasonography, Prenatal / Q000379:methods*