Triplex doppler ultrasonography to describe the uterine arteries during diestrus and progesterone profile in pregnant and non-pregnant bitches of different sizes

Hemodynamics of uterine vascularization is modified throughout pregnancy to meet the increasing demand of the growing fetuses and triplex doppler ultrasonography is widely used in human medicine to study the uterine arteries and assess the fetal and placental conditions. The aim of our study was to confirm this observation in the bitch, to evaluate differences between bitches of different sizes and to study abnormal pregnancies. Forty-four bitches were monitored during the estrous period to determine ovulation and every 10 days from ovulation to 50 days post-ovulation: the resistivity (RI) and pulsatility (PI) indexes of the right uterine artery were measured as well as usual assessment of fetal development and follow up of the luteal function. Thirty-three out of forty-four bitches were pregnant, including 6 abnormal pregnancies (resorption of more than 10% of the embryos). We also divided them in four weight categories: 8 were small (<10 kg), 13 medium (10-25 kg), 13 large (>25-40 kg) and 10 were giant breeds (>40 kg). We observed that RI and PI decreased over time and were significantly lower for pregnant bitches compared to non-pregnant ones from 30 days post-ovulation. In contrast, RI and PI did not significantly vary with the size of the bitches and we could not determine a significant impact of abnormal pregnancies either. In conclusion, we found no significant difference related to the size of bitches in the RI and PI. The only significant difference between pregnant and non-pregnant bitches was observed from 30 days post-ovulation.