Determination of the umbilical artery resistance index in pregnant Argentine Polo mares

Abstract

The objective of this work was to determine the resistance index (RI) of the fetal umbilical artery and its variation during pregnancy. The velocimetric values of the umbilical cord were evaluated in each of the ultrasound exams together with other parameters of fetal viability already known. Using a transabdominal ultrasound examination with a color Doppler ultrasound, the combined thickness of the uterus and placenta (CTUP), the depth and echogenicity of fetal fluids, fetal mobility, heart rate, diameter of the aorta, fetal sexing, and fetal position were evaluated. Observations were made on 20 Polo Argentino mares, aged between 4 and 12 years and in good body condition. Serial ultrasounds were performed every 30 days from the fifth to the eighth month of gestation. The results obtained from the ultrasounds performed showed that the RI decreases as the pregnancy progresses, which coincides with reports in human medicine. It is concluded that the determination of the RI by color Doppler ultrasound is a simple technique, which can be performed only with a gynecological stocks and suitable ultrasound equipment, the RI is expected to decrease in correlation with the progress of the pregnancy.