A longitudinal study of quantitative uterine blood flow with the use of color power angiography in appropriate for gestational age pregnancies

OBJECTIVE. The purpose of this study was to examine longitudinally changes in quantified blood volume flow in the uterine arteries during pregnancy wi th the use of color power angiography. STUDY DESIGN: Color power angiography was used to quantify volume flow in t he uterine arteries of 57 women with singleton uncomplicated pregnancies be tween 20 and 38 weeks' gestation. Comparisons were made between blood flow in the 2 arteries in relation to the location of the placenta. Linear regre ssion models were used to estimate gestational age derived volumetric chang es in these vessels. RESULTS: The diameter of the uterine arteries increased from 2.6 mm (SD, 0. 2 mm) at 20 weeks to 4.8 mm (SD, 0.7 mm) at 38 weeks of gestation. The tota l uterine artery blood volume flow increased from 513 mL/min (SD, 127 mL/mi n) at 20 weeks to 970 mL/min (SD, 193 mL/min) at 38 weeks. The rate of incr ease was maximum between 20 and 24 weeks (39 mL/min per week). The laterali ty of the placenta significantly affected the diameter and blood volume flo w in each uterine artery. The diameters on the ipsilateral side were signif icantly greater (by 10.8% +/- 2.4%) than the diameters on the contralateral side at all gestations (P < .05). Similarly, blood volume flow was signifi cantly greater (by 17.8% +/- 2.2%) on the ipsilateral side at all gestation s (P < .05). There were, however, no statistically significant differences between the vessel diameters and blood volume flow in those cases in which the placenta was central. Total uterine artery volume flow per kilogram of estimated fetal weight decreased from 1544 mL/kg per minute at 20 weeks to 296 mL/kg per minute at 38 weeks of gestation. CONCLUSION. Total quantified uterine artery blood volume flow increases whi le blood flow per kilogram of fetal weight decreases with gestation. Blood volume flow in the ipsilateral artery to the placenta was significantly hig her than that in the contralateral artery. Calculating total uterine artery volume flow by doubling the blood flow from 1 artery (as was previously do ne) may therefore either result in an over or underestimation, depending on the relationship between the vessel and the laterality of the placenta. Co lor power angiography is a simple noninvasive tool for determining uterine artery blood volume flow.