ACCELERATION TIME IN NORMAL FETAL UMBILICAL ARTERY AT TERM AND ITS RELATIONSHIP TO THE CORD-BLOOD HEMATOCRIT

The purpose of this study was to test the hypothesis that the accelera tion time (AT) of the fetal umbilical artery remains constant at term for normal pregnancies. In addition, we also examined whether the AT h as any correlation with umbilical cord blood hematocrit (Hct). In tota l, 539 normal-term fetuses with menstrual ages (MA) ranging from 37 we eks to 42 weeks were enrolled in a cross-sectional design. The AT of t he fetal umbilical artery was measured prior to delivery using a high- resolution, real-time Doppler scanner. All were delivered within 2 day s of the ultrasound examination. At parturition, blood from the umbili cal vein was collected and the red cell indices, including the Hct, we re determined. The results indicated that the mean values of AT of the umbilical artery remained constant during normal-term pregnancies fro m 37 weeks to 42 weeks, menstrual age (mean: 0.104 sec, SE: 0.001 sec, n = 539). Although the AT was thought to be affected by the Hct, the AT had no correlation with umbilical venous Hct (n = 539, r = 0.002,p > 0.05). This constant value of the AT may be used as a reference for fetal physiology and perinatal medicine. (C) 1995 John Wiley and Sons, Inc.