Experts in all aspects of equine wellness. Four partners lead the clinic with more than 75 years combined experience.
05/03/2025
Mini horse placenta vs. big horse placenta! 🥹✨
Assessing a mare’s placenta after foaling is a profoundly important, yet sometimes overlooked, step in safeguarding the health and long-term well-being of both mare and foal (no matter the size). This vital organ, responsible for sustaining life throughout the entire gestation period, holds crucial insights about the pregnancy and potential postpartum complications that may arise. But do you truly know what visual characteristics define a normal, healthy placenta? And perhaps more importantly, what specific signs or findings demand immediate attention from a veterinarian?
Once completely expelled, which should occur spontaneously within three hours following delivery, the placenta should be carefully laid out in a clear area and arranged into a “Y” or “F” shape. This allows for a thorough and systematic examination.
The placenta consists of two primary membrane layers: the chorioallantois, the thicker outer layer attached to the mare’s uterus, and the amnion, the thin inner membrane directly surrounding the foal. When inspecting the chorioallantois, the side adhered to the uterine wall should exhibit a rich, velvety, reddish appearance, indicative of healthy microcotyledons—structures facilitating the vital exchange of nutrients, waste, and gases. The opposite side should be smooth, pale pink, and display visible, branching blood vessels.
Key anatomical areas must be meticulously inspected for completeness, including the two horns which housed the developing fetus. The horn containing the majority of the pregnancy is typically larger and thicker. The central body connects these horns and leads towards the cervical star—a distinctively paler, avillous area where the placenta detached from the cervix, marking the foal’s passage.
𝗦𝗶𝗴𝗻𝘀 𝗼𝗳 𝗮𝗻 𝗔𝗯𝗻𝗼𝗿𝗺𝗮𝗹 𝗣𝗹𝗮𝗰𝗲𝗻𝘁𝗮
• Incompleteness: Missing pieces, particularly the tip of a horn, can be retained in the mare and lead to severe infection (metritis), laminitis, and even death.
• Thickening or Edema: Abnormally thick areas of the placenta can indicate inflammation or infection (placentitis).
• Discoloration: Abnormal colors such as pale, yellow, brown, or grey patches on the chorionic surface may suggest infection, poor blood supply, or meconium staining.
• Lesions or Tears: Beyond the expected tear at the cervical star, other damaged areas could indicate issues during pregnancy or foaling.
• Abnormalities of the Cervical Star: Thickening, discoloration, or exudate around the cervical star is a common indicator of ascending placentitis.
• Umbilical Cord Abnormalities: Examine the umbilical cord for excessive twisting, swelling, hemorrhage, or discolored areas.
• Meconium Staining: Yellowish-green staining on the placenta/amnion signifies the foal passed meconium in utero, typically a response to fetal stress during late gestation or foaling.
• Weight: A normal equine placenta weighs approximately 10-11% of the foal's body weight after birth.
Our team is readily available to provide expert guidance, help you understand what to look for, and offer comprehensive veterinary assessment and care should any concerns arise with your mare’s placenta or the health of her foal. Call us if you need us. 🙂
