Ultrasonographic Evaluation of the Fetus and Intrauterine Environment in Healthy Mares During Late Gestation

Abstract

Mares with uncomplicated pregnancies (n = 33) underwent transabdominal sonography to evaluate fetal well-being, obtain measurements of fetal size and characterize the intrauterine environment. Data from the last examination obtained prior to parturition were used for statistical analysis. All mares had one active fetus with good fetal tone. The maximal vertical depth of amniotic fluid (7.9 + 3.5 cm) was less than allantoic (13.4 + 4.4 cm) and fewer echogenic particles were detected in amniotic fluid. The maximal uteroplacental thickness was 1.38 k 0.23 cm (retrospective) and 1.15 ++ 0.24 cm (prospective). In 3 mares small anechoic spaces were imaged between the uterus and placenta. Fetuses had a regular cardiac rhythm with a mean heart rate of 75 2 7 beatslminute and breathing movements. The diameter of the fetal aorta (mean = 22.8 f 2.15 mm) was significantly correlated with neonatal foal weight (P < 0.0008, r = 0.72) and maternal prepartum weight (P < 0.002, r = 0.86). This information on the normal intrauterine environment and fetal well-being can be used to develop a biophysical profile specific for the equine fetus. V e t e r i n q Radiology

Transabdominal ultrasonographic evaluation of fetal well-being in the late-term mare and cow

“…In cows, sometimes it is possible to restrain the dam only by holding her head (Buczinski, 2009), but according to other authors and in the authors' experience, for safety reasons horses and cows should be placed in a stock wherever they are examined (Reef et al, 1995(Reef et al, , 1996Reef, 1998;Baska-Vincze et al, 2013.…”

“…On the one hand, they could observe long resting periods during the 10-min examinations when the calves did not make any movement, so fetal activity was graded as zero without any negative consequences. In horses, fetal activity strongly correlates with fetal wellbeing (Reef et al, 1995(Reef et al, , 1996Reef, 1998). In the equine fetus, thoracic aortic diameter is a sensitive predictor of birth weight but in cattle the correlation coefficient is not so high (Buczinski et al, 2011).…”

“…Then the scores were summed up. A low score was a definite indication of an impending negative outcome; however, a high score did not provide assurance that the delivery would have a positive outcome (Reef et al, 1995(Reef et al, , 1996Reef, 1998). This BPP became the 'gold standard' for transabdominal ultrasonography for many years in the examination and treatment of pregnant mares in the clinical practice.…”

Sonographic parameters for assessment of fetal well-being in mid-gestation in german Thoroughbred mares

“…These particles consist of mucoproteins, calcium phosphate and other mineral deposits, and likely result from fetal kidney function (Bucca et al 2005, Adams-Brendemuehl andPipers 1987). Often FFP are only visible after vigorous fetal movement (Reef et al 1995).…”

“…To measure the CTUP with transrectal ultrasound, a linear transducer is positioned cranial of the cervical-placental junction and moved in lateral direction until the middle branch of the uterine artery is visible ventral from the uterine body. The CTUP then is measured between the middle branch of the uterine artery and the allantoic fluid (Reef et al 1995)). Measurement of the ventral part of the uterus was found to give more accurate information than when measurements were done of the dorsal part, because of the physiological edema in the dorsal part .…”