Hi there! It’s Winnie the Clinic Mouse, and guess what? I’m a quintuplet, which means I have four siblings who were born at the same time as me! It’s quite a busy and exciting life, having so many siblings. But that’s not all—one of our veterinarians, Dr. Carter, is a twin! It’s fascinating to see how different species experience multiple births!

In the world of mammals, many of us can have multiple babies at once. For mice like me, having a bunch of siblings born together is pretty normal. But for horses, it’s a whole different story. While some mammals handle multiple births with ease, twin pregnancies in horses can be very dangerous.

Causes of Twin Pregnancies

Twin pregnancies in horses occur when two ova are fertilized simultaneously. This happens when a mare double ovulates or releases two eggs. While this may sound like an advantage for breeding, it often leads to complications.

Risks Associated with Twin Pregnancies

The main risks of twin pregnancies in horses include:

• Abortion: The majority of twin pregnancies end in early embryonic loss. The limited space and nutrient availability within the uterus make it challenging for both embryos to survive.
• Dystocia (difficult birth): If the pregnancy continues to term, the mare is at a higher risk of dystocia, which can endanger both the mare and the foal.
• Abnormal Foals: Even if twins are carried to term, they are often born weak and underdeveloped due to the shared resources in the womb.
• Mare Health Issues: The mare can suffer from complications such as retained placenta, which can lead to severe infections.

Diagnosing Twin Pregnancies

• Early detection of twin pregnancies is crucial. This is why the 14 day pregnancy check after breeding is so important. At this time, we can diagnose and manage twin pregnancies.
• Ultrasound Scanning: A veterinarian can perform an ultrasound around 14 to 16 days post-ovulation to detect multiple embryos. If twins are identified, steps can be taken early to manage the situation.

Management of Twin Pregnancies

Once twins are detected, it is highly recommended that the mare does not continue to carry both embryos and that one embryo is removed, or the pregnancy is terminated due to the high risk to the mare and foals in twin pregnancies.

• Selective Reduction: This is the most common and effective method. One embryo is manually reduced via ultrasound guidance, allowing the remaining embryo a better chance to develop normally.

Twin pregnancies in horses present significant challenges and risks, but with early detection and appropriate management, these risks can be mitigated. Understanding and managing twin pregnancies effectively can lead to successful breeding outcomes, despite the inherent difficulties. If you plan on breeding your mare, make sure you follow the recommended pre- and post-breeding appointment plan from your veterinarian. It’s a lot of appointments, but for very good reason!

Until next week,

~Whinny

P.S. Have you listened to all of the breeding episodes on my Doc’s podcast? They have a number of different episodes about various aspects of breeding, and you won’t want to miss any of them! You can find them over on the Podcast Page of my website, or subscribe to Straight from the Horse Doctor’s Mouth on Apple Podcasts, Spotify, or wherever you get your podcasts!