Abstract
The present study aimed to determine the hemodynamic changes within uterine and umbilical arteries during different months of pregnancy. A total of 180 Egyptian buffaloes were scanned transrectally by B-mode and Pulsed Wave Doppler ultrasonography. Selected animals were chosen to represent various stages of pregnancy from the 2nd up to the 10th month of pregnancy; 20 animals were used for each month. Both Pulsatility index (PI) and Resistance index (RI) of the ipsilateral uterine artery showed a nearly constant pattern until the 5th month of pregnancy. Values of both indices significantly decreased on ward. However, TAMV showed non-significant changes or slightly increased values were observed on the 2nd, 3rd, and 4th months of pregnancy, followed by significantly increased values as pregnancy progressed. BFVol values showed a nearly similar pattern as that of TAMV, where non-significant changes were observed during the 2nd and 3rd months of pregnancy, followed by significantly increased values onward. In addition, the diameter of the ipsilateral uterine artery (UAD) increased dramatically during different months of pregnancy. The umbilical cord could be detected for the first time at day 40 of pregnancy, along with the spectral waveform pattern. Pulsatility index of the umbilical artery (Um PI) significantly increased across the examination period. Whereas, Resistant index (Um RI) remained relatively constant throughout different months of pregnancy. Time average maximum velocity (Um TAMV) showed non- significant changes till the 4th month, then after increased significantly at the 5th and 8th months of pregnancy. Blood flow volume (Um BFVol) increased significantly during the 2nd, 3rd, 5th and 8th months of pregnancy. Cross-sectional diameter of the umbilical artery (Um D) significantly increases during the 3rd and 8th months of pregnancy. Altogether, the present results show that, Color Doppler Ultrasonography is a successful tool for evaluation of uterine and umbilical blood flow changes during different months of pregnancy in Egyptian buffaloes. The normal changes in uterine and umbilical blood flow indices can serve as the basis for evaluating abnormal pregnancies

Key words: Color Doppler, uterine blood flow, umbilical blood flow, pregnancy, buffaloes.