Equine uterine blood flow during pregnancy

Uterine blood flow of four Trotter mares and one Haflinger mare, aged 4 to 19 years, were examined weekly from the fifth week of gestation unlit birth using colour Doppler sonography. Perfusion was characterised by the pulsat ility index (Pi) and the average blood flow velocity (Vmean). Diameter of t he uterine artery was registrated once a month. During pregnancy changes in uterine blood flow were similar in all mares. O n the pregnant side the pulsatility index decreased by half. Only at the be ginning of gestation the PI on the nonpregnant side was significantly highe r. From the 11(th) week of pregnancy onwards values did not differ between the two sides. The average blood flow velocity in contrast was similar on b oth sides for the whole length of pregnancy. Vmean increased continuously s even times from 25 cm/s to 175 cm/s. The diameter of the uterine artery inc reased constantly on both sides from 3 mm to 15 mm. One of the 5 mares abor ted in week 36 because of an infection with EHV-I. Blood flow in this mare was not different from that: in the other animals with normal pregnancies.