Doppler ultrasonographic studies of the uterine blood flow in mares

The uterine arteries of ten mares, from which endometrial biopsies had been taken and graded from category I to category Ill, were investigated on a d aily basis for an entire cycle using transrectal Doppler ultrasonography. A ll mares showed a similar cyclic variation in uterine blood flow. Resistanc e to blood flow in the uterine artery was highest in the periovulatory peri od. The mares of category IIb and III (group B) had higher values of uterin e artery impedance when compared to those mares in category I to IIa (group A). Some of the mares in group B showed an absence or reverse in diastolic blood flow. These results agree with similar data obtained in women, where there is discussion as to whether reduced uterine blood flow can cause inf ertility.