Natural outcome and ultrasonic identification of equine fetal twins.
Abstract: The natural outcome of bilateral twins (one in each uterine horn) that were viable on Day 40 was studied in 15 pony mares. Fetuses were monitored by transrectal ultrasonography until the outcome was determinable. One fetus (2 mares) or both fetuses (8 mares) died (cessation of heartbeats) during Months 2 and 3. Loss of fetuses was externally observed in 4 additional mares during the late fetal stage (Months 8 to 11); 2 mares lost 1 fetus and 2 lost both fetuses. Birth of 2 live foals occurred in only 1 of 15 mares (7%) First day of detected apposition between portions of the 2 allantochorions was studied daily on Days 40 to 51 in 7 of the 15 mares. Apposition was first detected on mean Day 46.3 (standard deviation: +/-3.1). In these 7 mares, death of 1 fetus (2 mares) or both fetuses (2 mares) occurred 1 or 2 days after the first day of apposition of allantochorions; no deaths occurred before the day of apposition. Each mare with loss of one fetus during this time gave birth to a living foal. The only structure indicative of twins that was consistently detected ultrasonically during all examinations was the common membrane resulting from the area of apposition between the 2 allantochorions. The common membrane is herein designated as the twin membrane because of its apparent diagnostic potential even in late pregnancy when the presence of the 2 fetuses may not be detected directly. Thickness of the twin membrane reached approximately 3 mm at Month 7 and thereafter gradually increased to 15 mm near the end of pregnancy. Two layers of the membrane (1 for each allantochorion) became distinct at Month 6 and Month 8 with 5.0 MHz and 3.5 MHz transducers, respectively; the 2 layers were separated by a hypoechogenic layer.
Publication Date: 1994-01-01 PubMed ID: 16727471DOI: 10.1016/s0093-691x(05)80041-xGoogle Scholar: Lookup
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- Journal Article
Summary
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This research investigates the natural progression of twin foal pregnancies in pony mares using ultrasonic technology. They found that the survival rate of fetal twins was only 7% and a specific common membrane between the fetuses could be an important early indicator of a twin pregnancy.
Research Methodology
- The researchers studied the viability of bilateral twins (one fetus in each uterine horn) in 15 pony mares.
- The fetuses were monitored using transrectal ultrasonography from Day 40 until the outcome of the pregnancy was known.
Results and Findings
- One fetus in two mares and both fetuses in eight mares died between Months 2 and 3.
- Four additional mares experienced fetal loss in the late fetal stage (Months 8 to 11). Of these, two mares lost one fetus and two lost both fetuses.
- Only one mare (7% of the subjects) gave birth to two live foals.
Analysis of allantochorions
- The researchers studied the first day of apposition (contact or nearness) between parts of the two allantochorions (fetal membranes) in seven of the 15 mares. Apposition was first noticed on average on Day 46.3.
- Death of one or both fetuses occurred one or two days after the first day of apposition; no fetal deaths occurred before apposition.
- Mares that lost one fetus during this period eventually birthed a living foal.
Ultrasonic Identification
- The researchers identified a common membrane between the two allantochorions, which was consistently found during ultrasound exams and could serve as an indicator of twin fetuses even in late pregnancy.
- The thickness of this “twin membrane” reached around 3 mm at Month 7 and increased gradually to 15 mm near the end of pregnancy.
- The separate layers of the membrane (one for each allantochorion) became distinguishable at Month 6 and Month 8 using different types of transducers.
Cite This Article
APA
Ginther OJ, Griffin PG.
(1994).
Natural outcome and ultrasonic identification of equine fetal twins.
Theriogenology, 41(5), 1193-1199.
https://doi.org/10.1016/s0093-691x(05)80041-x Publication
Researcher Affiliations
Citations
This article has been cited 2 times.- Salem SE, Sinnott A, Roach JM, Verheyen KLP, de Mestre AM. Mixed-Effects Modelling of the Risk Factors Associated with Multiple Pregnancies in Thoroughbred Mares. Animals (Basel) 2022 Jul 20;12(14).
- Raggio I, Lefebvre RC, Poitras P, Vaillancourt D, Goff AK. Twin pregnancy experimental model for transvaginal ultrasound-guided twin reduction in mares. Can Vet J 2008 Nov;49(11):1093-8.
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