29/08/2025
Fun Facts for Friday 👌
🧬 1. Anatomy of the Canine Uterus and Uterine Horns
• Female dogs have a bicornuate uterus, meaning it has two long uterine horns and a relatively short uterine body.
• Each uterine horn extends from the body of the uterus and connects to an o***y via a fallopian (uterine) tube.
• The horns are where embryos implant and develop during pregnancy.
📈 2. Function of the Uterine Horns in Pregnancy
• After ovulation, fertilisation occurs in the oviduct.
• The fertilised ova (zygotes) migrate down the oviducts into the uterine horns within 5–8 days post-ovulation.
• Implantation typically occurs around day 17–21 of gestation.
• The embryos space themselves out evenly in both uterine horns via uterine contractions, a process called embryonic migration.
🐾 3. Changes During Pregnancy
Early to Mid-Gestation (Days 1–30)
• Uterine horns become more vascular and edematous.
• Embryonic vesicles are visible by ultrasound around day 18–21.
• Horns begin to enlarge where embryos are implanted.
Mid to Late Gestation (Days 30–63)
• The fetuses grow rapidly; the horns expand significantly.
• The uterine horns may twist or curve to accommodate the growing fetuses.
• Palpation becomes more difficult in late gestation as the horns lose their segmented feel and become fluid-filled.
🤰 4. Role During Whelping
• During parturition (labour), the uterine horns contract rhythmically to push each puppy toward the uterine body and then into the cervix and vaginal canal.
• Puppies are typically delivered alternately from the left and right horns, though not always evenly.
• After each delivery, contractions continue to expel placentas and prepare the next fetus for delivery.
🧪 Clinical Relevance
• Ultrasound and Radiography:
• Ultrasound is useful early in pregnancy to assess uterine horn content and fetal viability.
• Xrays can be done after day 45 to count skeletons, although this is not a common practice in the UK, and I personally question the practice.
• Uterine Horn Abnormalities:
• Pyometra (infection of the uterus) can involve one or both horns.
• Uterine torsion or rupture, though rare, are serious conditions during pregnancy.
🐶 Key Notes for Breeders or Vets:
• Monitor closely for signs of dystocia (difficulty in labour), especially if the horns are overdistended (e.g., large litter or singleton pregnancy).
• It’s common for a slight asymmetry between horns (one may carry more pups).
• After whelping, the uterine horns gradually return to pre-pregnancy size over a few weeks.
Photo courtesy of Blue Pearl Pet Hospital
