Twinning as a Cause of Abortion – Species

'Twinning' is a very common cause of abortion in:

Correct Answer: Mare

In the mare, twinning (twin pregnancy) is a very common cause of abortion. Unlike cattle where twin pregnancies sometimes proceed to term, the uterus of the mare cannot adequately support two fetuses, leading to abortion of both.

Why Twinning is Problematic in Mares

• The mare has a T-shaped uterus with limited uterine capacity — not suited for two fetuses.
• Twin pregnancies in mares lead to abortion (usually at 7–9 months), premature births, stillbirths, or birth of weak foals that die shortly after.
• Management: Twins are routinely detected by ultrasound early and one vesicle is manually crushed (twin reduction) to save one pregnancy.

Contrast With Other Species

• Sow: Litter-bearing animal — multiple fetuses are normal.
• Bitch: Also litter-bearing — twinning is normal.
• Sheep: Twins are common and usually well-tolerated.
• Mare: Designed for singleton pregnancies — twinning is pathological ✔