Ultrasonographic assessment of fetal well‐being during late gestation: development of an equine biophysical profile

Abstract

Mares with complicated pregnancies (illness, problems at parturition or delivery of an abnormal foal, n = 30) were scanned transabdominally from 298 days gestation to term in order to measure fetal size, evaluate fetal well-being and characterise the intrauterine environment. The results of the last scan obtained prior to parturition were compared to normal data obtained from fetuses of comparable gestational age to develop a biophysical profile specific for the equine fetus. Twelve mares produced a normal foal (positive outcome) and 18 mares delivered 19 abnormal foals (negative outcome). Both fetuses that were inactive throughout the entire scan and 4 of 5 fetuses with heart rate abnormalities were abnormal at birth. Three of 4 fetuses surrounded by decreased allantoic fluid quantities had a negative outcome. All mares with large anechoic spaces between the uterus and placenta (n = 3) and/or thickened uteroplacental units (n = 5) delivered abnormal foals. There was a significant correlation between fetal aortic diameter and neonatal foal weight in these complicated pregnancies (P<0.0001, r = 0.85). Fetal aortic diameters were predicted from maternal weight and 6 fetuses had smaller than predicted aortic diameters, all with negative outcomes. A biophysical profile of the equine fetus from 298 days gestational age to term was developed that included 6 factors related to pregnancy outcome: fetal heart rate, fetal aortic diameter, maximal fetal fluid depths, uteroplacental contact, uteroplacental thickness and fetal activity. The profile proved informative about fetal well-being, perinatal morbidity and perinatal mortality. A low score was a definite indication of an impending negative outcome; however, a high score was not assurance of a positive outcome. The utility of such a biophysical profile and future directions for research are discussed.

Fetal death: comparative aspects in large domestic animals

“…During the evaluation of the late gestational fetus, a so-called biophysical profile score is made that encompasses the FHR, gross fetal movements, fetal aorta diameter, fetal fluid quality and the utero-placental unit. Using this profile, Reef et al (1996) were able to identify "at risk" foals (with a low biophysical profile score) that were later born compromised or even dead. However, a good biophysical profile score did not guarantee a positive outcome.…”

“…In both cattle and horses, the trans-rectal approach is preferred during the first 3 months of gestation. Thereafter, the pregnant uterus tends to drop deeper into the abdomen such that it is difficult to visualise all parts of the fetus (Reef et al, 1996;Breukelman et al, 2004). The trans-abdominal approach is, therefore, preferred during late gestation in cattle and horses, and at all stages in small ruminants and pigs (Cohen et al, 1997).…”

“…Ultrasonographic monitoring of the fetus and placenta using the criteria published by Adams-Brendemuehl and Pipers (1987) and Reef et al (1996) has been recommended for mares nearing the end of gestation but considered to be at risk of abortion. During the evaluation of the late gestational fetus, a so-called biophysical profile score is made that encompasses the FHR, gross fetal movements, fetal aorta diameter, fetal fluid quality and the utero-placental unit.…”

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

“…The presence of FFP in the allantoic fluid has been described from the fourth month of gestation to full term (Bucca et al 2005). It should be noted, however, that FFP are often only visible after vigorous fetal movement (Reef et al 1996). An increase in number of FFP has been reported in case of placentitis Sertich 1994, Renaudin et al 1999).…”

“…During activity of the fetus, FHR values were 155 ±11.18 beats/min for month 4 of gestation, 142 ± 8.52 for month 5, 139 ±11.72 for month 6, 129 ± 7.08 for month 7, and 125 ±11.54 for the month 8. Fetal heart rates that differ more than 2 times the standard deviation from the threshold values as indicated above were considered abnormal (Reef et al 1996). Ultrasonographic parameters that are used to assess the fetal environment include the evaluation of the combined thickness of uterus and placenta (CTUP), and the echogenicity of fetal fluids including the existence of echogenic free floating particles.…”