Establishment of a new equation to estimate gestational age in female dogs.

The objectives of this study were to propose a statistical model to predict the behaviour of the thickness of the uteroplacental junction as a function of the gestation period in female dogs and to determine the relationship between the thickness of the placenta and gestational age in healthy female dogs whose pregnancies had elapsed without maternal-fetal alterations. Eight Border Collie female dogs were selected, aged 3-6 (4.48 ± 0.89) and weighing 16-22 kg (19.06 ± 1.9 kg). Female dogs with gestational ages from 20 to 62 days were examined weekly using B-mode ultrasonography. Ultrasound measurements of the uteroplacental junction were organized into four distinct groups: GT1 (27-36 days of gestation), GT2 (37-46 days of gestation), GT3 (47-56 days of gestation) and GT4 (57-62 days of gestation). Based on multiple linear regression, a statistical model was proposed to predict the behaviour of the thickness of the uteroplacental junction (y) as a function of the length of gestation (x) in female dogs, where b0 is the intercept (linear coefficient) and bp is the slope of the predictors. The analysis relating GT, age and weight could predict placental thickness and resulted in a statistically significant model [F(1,28) = 153,736; p < .001; R2 = .846], but only that relating the length of pregnancy (ß = .92; t = 12.399; p < .001) predicted the thickness of the placenta according to the equation y = b0 + bp.x1 [(thickness in cm) = ß -0.3 + 0.019 × (gestation time in days)]. Only in GT4 was there no correlation between placentas within the same pregnancy (p > .05). Based on the close relationship between the development of the uteroplacental junction thickness during pregnancy and gestational age, it is possible to develop a new tool to complement gestational ultrasound evaluation in female dogs. This is important because it allows better placental evaluation in the search for significant alterations that could compromise maternal-fetal health.

Spectral Doppler ultrasound in the placental development of Mangalarga Marchador mares.

The aim of the study was to correlate the spectral index of the right and left uterine arteries with equine placental development in mares with advanced pregnancies. We examined 32 multiparous Mangalarga Marchador mares with gestation of 150-240 days. During pregnancy, the pulsatility index (PI) and resistance index (RI) of the uterine arteries were obtained using spectral Doppler ultrasonography, and the combined uteroplacental thickness was obtained monthly using B-mode ultrasonography. The combined uteroplacental thickness correlated with gestational time of up to 13 years of age, and the significant difference was observed from the sixth month onwards. The CUPT stayed within the ideal measurements for this breed and for this gestational period. There was no correlation of CUPT with PI, however a negative and significant correlation of the RI was observed. The resistance index differed significantly among age groups, and the RI of the left uterine artery tended to decrease in all age groups. Furthermore, only RI differed significantly between the medians of gestatinal age. The left PI dropped in older mares. Thus, there an increased blood perfusion in the uterine arteries of mares with advanced pregnancies and among different age categories during placental and fetal physiological development.

Transrectal ultrasonography for measuring of combined utero-placental thickness in pregnant Mangalarga Marchador mares.

This study aimed to measure the physiological changes in the combined utero-placental thickness (CUPT) during the course of normal pregnancy in Mangalarga Marchador mares. Transrectal B-mode ultrasonography was used to measure CUPT in 42 pregnant mares with a mean age, 8.7 (±3.5 years). CUPT was measured every month from 150 days of gestation until delivery. CUPT was expressed as an average of three measurements of the distance (mm) between the middle part of the uterine artery and the allantoic fluid. A General Linear Model was used to evaluate the major effects of the chronological age and stage of gestation on CUPT in mares. The coefficient of determination (R2) was 0.571 (P < 0.001). There was no correlation between CUPT and the chronological age of the mares, however, there was a positive correlation between CUPT and the stage of gestation, which an accounted for 29.6% of the observed variation. CUPT significantly increased during the gestational period from 210 to 240 days and 270-300 days. These results showed CUPT increased as pregnancy advanced in the Mangalarga Marchador mares. In conclusion these effects of the stage of pregnancy on the increase in CUPT showed a physiological parameters of ultrasonography evaluation of the placenta in Mangalarga Marchador mares.