Ultrasonographic Evaluation of Equine Fetal Growth Throughout Gestation in Normal Mares Using a Convex Transducer

Abstract

It has not been common to perform regular ultrasound examination of the fetus in equine practice, due to the increasing volume of the uterus caused by fetal development. The convex three-dimensional transducer is bulb-shaped and is able to observe wide areas. In addition, its operation is simple, making it easy to create appropriate angles for various indices using a transrectal approach. The aim of this study was to measure Thoroughbred fetal growth indices throughout gestation using a convex transducer and to clarify the detectable period of some indices for clinical use. We demonstrated changes in fetal indices, such as crown rump length (CRL), fetal heart rate (FHR), fetal eye and kidney and the combined thickness of uterus and placenta (CTUP). CTUP increased from 30 weeks of gestation, and FHR peaked at 8 weeks and then decreased to term. CRL could be observed until 13 weeks due to its wide angle, longer than in previous reports. Fetal eye and kidney could be observed from 10 and 28 weeks, respectively, and these increased with pregnancy progress. The present results showed the advantage of transrectal examination using a convex transducer for evaluation of normal fetal development. Although ultrasonographic examination in mid- to late-gestation is not common in equine reproductive practice, our comprehensive results would be a useful basis for equine pregnancy examination.

Ultrasonographic findings associated with normal pregnancy and fetal well‐being in the bottlenose dolphin (Tursiops truncatus)

“…[25][26][27][28] Such evaluations help predict positive versus negative outcomes and aid in understanding of pregnancy failure pathophysiology. [29][30][31] As dolphins and horses have a similar diffuse epitheliochorial placenta, equine reproductive ultrasound provides a reasonable species model. 32,33 The purpose of this study was to expand upon early work in gestational ultrasound of bottlenose dolphins [34][35][36] and develop a reproducible protocol for ultrasonographic monitoring of fetomaternal health in the bottlenose dolphin, reporting normal measurements and descriptive findings correlating with a positive outcome.…”

“…Standard ultrasonographic methodology to assess fetal growth and well‐being has been established in humans and horses . Such evaluations help predict positive versus negative outcomes and aid in understanding of pregnancy failure pathophysiology . As dolphins and horses have a similar diffuse epitheliochorial placenta, equine reproductive ultrasound provides a reasonable species model .…”

A regression model including fetal orbit measurements to predict parturition in Standardbred mares with normal pregnancy

“…The equine fetal ocular measurements were investigated in several studies: longitudinal diameter [15,16], both longitudinal and transverse diameter [12], circumference and area of vitreous body [13]. In the previous studies [12,[14][15][16]19], the two calipers were positioned excluding the anterior chamber to measure the transverse diameter. In this study, the transverse diameter was measured including the anterior chamber from the cornea to the retina as described by other studies about the ultrasonographic ocular measures of the growing foal [41,42] and adult horse [43].…”

“…In equine reproduction, transrectal ultrasonography is the most important technique to evaluate the pregnancy; it is a quick and easy on-farm procedure that is widespread among reproduction specialists. With transrectal ultrasonography the fetal orbit is easily accessible in the last month of pregnancy, and its measurement has been widely used to estimate both fetal growth [11][12][13][14] and gestational age [15][16]. Turner et al [15] and Hartwig et al [16] developed a formula for predicting parturition or gestational age in ponies and Crioulo mares, using ocular longitudinal diameter.…”

Medición ultrasonográfica del largo del cuerpo vítreo fetal equino para predecir los días para el parto en caballos Pura Raza Española

“…Differences in growth patterns were described in various studies, evidencing either a linear growth pattern in Crioulo horses (Hartwig et al 2012), light horses (Kahn & Leidl 1987), and standardbreds, (Lanci et al 2018) or a curvilinear pattern in Dutch Warmbloods (Hendriks et al 2009), light horses, ponies (Turner et al 2006), and Thoroughbreds (Murase et al 2014). Although different growth patterns may be due to the methodology implemented in each study, an evident variation in size and development pattern of the fetal ocular orbit has been pointed out, even in breeds of similar size (Kahn & Leidl 1987;Renaudin et al 2000;Turner et al 2006;Hendriks et al 2009, Hartwig et al 2012.…”