Maternal cerebral blood flow changes in pregnancy.
OBJECTIVE
This study was undertaken to determine blood flow changes in the large cerebral arteries during normal pregnancy.


METHODS
Ten healthy pregnant volunteers underwent velocity-encoded phase contrast magnetic resonance imaging at 4 time intervals: 14 to 16, 28 to 32, and 36 to 38 weeks' gestation, and at 6 to 8 weeks' postpartum. Analysis consisted of serial paired Student t tests, with P<.05 considered significant.


RESULTS
By using postpartum values for comparison, cerebral blood flow decreased by 14 to 16 weeks in the middle cerebral artery (P<.001), but was not significantly changed in the posterior cerebral artery. Significant decreases occurred in both the middle (P<.0001) and posterior (P=.002) cerebral arteries in late pregnancy.


CONCLUSIONS
An approximately 20% reduction in large artery cerebral blood flow occurs during normal pregnancy, secondary to changes in velocity, whereas the area of these vessels remains unchanged. These findings may represent generalized vasodilatation of downstream resistance arterioles, assuming constant blood flow at the tissue level.
Zeeman
Gerda G
GG
Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas, Texas, USA. g.g.zeeman@isala.nl
Hatab
Mustapha
M
Twickler
Diane M
DM
D000328:Adult; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D020768:Middle Cerebral Artery / Q000502:physiology; D020769:Posterior Cerebral Artery / Q000502:physiology; D049590:Postpartum Period / Q000502:physiology; D011247:Pregnancy / Q000502:physiology*; D011446:Prospective Studies