Diagnosing pregnancy is a valuable management tool used by small ruminant producers to allow for better nutritional management, rebreeding management, and/or culling decisions of subfertile and infertile females. Identifying ewes carrying multiple fetuses is also useful to producers so that these animals can be fed appropriately to avoid pregnancy toxemia.
母羊经腹超声检查
At approximately 55 days of gestation, a transabdominal ultrasonogram of a pregnant ewe typically reveals distinct, developing placentomes, which are the functional units of the small ruminant placenta. At this stage, placentomes are becoming more prominent and are often one of the most recognizable structures on the scan. Placentomes appear as paired, echogenic to moderately echogenic, C‑shaped or O-shaped structures within the uterine lumen.
Courtesy of Dr. Clare Scully.
Transabdominal ultrasound of twin embryonic vesicles at 35 days’ gestation in a ewe. At approximately 35 days, a transabdominal ultrasonographic examination of a ewe with a twin pregnancy typically reveals two distinct fluid‑filled embryonic vesicles within the uterine lumen. These appear as anechoic (black) round to oval structures, each surrounded by a thin, smooth, echogenic (bright) rim representing the developing trophoblastic membranes.
Courtesy of Dr. Clare Scully.
Transabdominal ultrasonography is the most common tool used to diagnose pregnancy in small ruminants. Several distinct ultrasonographic techniques are used:
A-mode: The transducer emits ultrasonographic waves that penetrate abdominal structures and are reflected when they meet high acoustic impedance interfaces (eg, fluid). A-mode ultrasonography is a quick, convenient, and simple technique; however, it cannot predict fetal number or viability.
Doppler: Doppler devices use the Doppler shift principle to detect fetal heartbeats and blood flow in uterine and fetal vessels.
B-mode: This method provides visible, real-time imaging of the uterus. B-mode ultrasonography is an accurate, rapid, safe, and practical means for diagnosing pregnancy, determining fetal number, and estimating gestational age.
Accuracy for pregnancy diagnosis using transabdominal ultrasonography is > 80% after 31 days of gestation. What ultrasonography shows depends on the number of days of gestation:
< 35 days of gestation: hyperechoic fetus in fluid-filled (anechoic) uterine horn
> 35 days of gestation: fetus in fluid-filled uterine horn and “C”-shaped or doughnut-shaped placentomes detectable (see )
45–50 days of gestation: C-shaped or doughnut-shaped placentomes are very obvious; best time for fetal number determination
After 50 days of gestation: C-shaped or doughnut-shaped placentomes are very obvious but because of the size of the fetus(es), determining fetal number is not possible (see ).
了解更多信息
Bayne JE, van Santen E, Cole RC. Ultrasonographic analyses of fetal gastrointestinal characteristics and correlations with gestational age and maturity in sheep. Small Rumin Res. 2025;246:107485.
Roberts, Jennifer. Pregnancy diagnosis in small ruminants. In: American Association of Bovine Practitioners 55th Annual Conference Proceedings. 2023.
