Middle cerebral artery peak systolic velocity in monochorionic and dichorionic twin pregnancies.
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.
Dashe
Jodi S
JS
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
Ramus
Ronald M
RM
Santos-Ramos
Rigoberto
R
McIntire
Donald D
DD
Twickler
Diane M
DM
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*