Red-bag delivery – a true emergency

Within the uterus of a pregnant mare the foal lies within two membranes: the amnion (inner membrane) and the allantois (outer membrane). It is through the allantois that oxygen, nutrients and waste products are exchanged between maternal and fetal blood.

During normal delivery, the allantois ruptures at the cervix, but remains attached to the uterus during the delivery process to continue provision of oxygen to the foal.

Subsequently, the water breaks, the amnion will become visible (pictured), and eventually the foal is delivered within or partially within the thin white amnion. This membrane easily breaks during parturition or when then foal starts moving. The allantois (or the placenta) detaches from the uterus and is expelled after the delivery of the foal.

In the case of red bag delivery, the allantois does not break, and the foal is delivered within both membranes. This can be seen as a red, thick membrane protruding from the vulva: the so called “red bag”.

When this occurs, the allantois is no longer attached to the uterus, and there is no more oxygen exchange between the foal and mare. These foals may become compromised from lack of oxygen and thus, it is very important to deliver the foal as soon as possible.

This allantoic membrane is tougher than the amnion and is difficult for the foal to break. Therefore, as soon as you see a “red bag”, it should be manually opened using your fingers or a pair of scissors.

The reason for red bag delivery is not always clear, but infection (placentitis) is a common cause. Foals born from red bag delivery have increased risks of illness early in life. It is therefore recommended that both mare and foal are both examined by a veterinarian after such an event.

Red bag delivery is one of the conditions were having a vet in attendance during foaling can help ensure a positive outcome.


Picture: A foaling mare. The white amniotic membrane is coming out, and if you look closely, you can see the hooves through the membrane.