Retained Placenta in Mares: Emergency Signs, Treatment, and Laminitis Prevention

By Dr Duncan Houston

A retained placenta in a mare is not a minor delay. It is one of the most time-sensitive emergencies in equine reproduction.

The difference between a straightforward recovery and a life-threatening complication often comes down to hours, not days.

Many owners underestimate this condition because it can look deceptively calm at the start. The mare may appear comfortable, the foal is nursing, and the only visible issue is that the placenta has not passed.

Internally, however, inflammation, bacterial contamination, and toxin release can begin quickly. This is what drives the real risk.

Quick Answer

A retained placenta occurs when a mare does not pass the full fetal membranes within 3 hours after foaling. This is an emergency because it can rapidly lead to uterine infection, systemic illness, and laminitis. Immediate veterinary treatment, including oxytocin, uterine lavage, and aggressive laminitis prevention, is critical to protect the mare.

What Is a Retained Placenta?

After foaling, the placenta should be expelled completely, usually within 1 to 3 hours.

If any portion remains attached beyond this point, it is classified as a retained placenta.

Key point

This is not about how much placenta is retained. Even a small piece can trigger serious complications.

Common location

The most frequent site of retention is the non-pregnant horn of the uterus. This area is more difficult to contract effectively, which is why tissue often remains there.

Why Retained Placenta Is So Dangerous

This is where clinical understanding matters.

The placenta is no longer a sterile structure once separated from the foal. When retained, it becomes a source of bacterial growth and toxin release.

What can happen next

• uterine infection develops rapidly

• bacteria and toxins enter the bloodstream

• systemic inflammation increases

• blood flow to the feet is disrupted

• laminitis risk rises significantly

Clinical insight

Laminitis is not a secondary concern. It is one of the primary reasons retained placenta is treated as an emergency.

How Quickly Does Risk Increase?

0 to 3 hours

Normal window for expulsion

3 to 6 hours

Retention confirmed, intervention needed

Beyond 6 to 8 hours

Risk of infection and systemic complications increases

Beyond 8 to 12 hours

Laminitis risk becomes significant

Practical rule

If the placenta is not fully passed by 3 hours, treat it as urgent.

What Should You Do Immediately?

Step 1: Call your veterinarian

Do not delay.

This is not something to monitor overnight or reassess later.

Step 2: Do not pull the placenta

This is one of the most important rules.

Pulling can cause:

• tearing of the uterus

• hemorrhage

• incomplete removal

• worsening inflammation

What you can do instead

If the placenta is hanging:

• tie it up into a loose knot to prevent the mare stepping on it

• keep it clean and off the ground

Do not cut it and do not apply traction.

Veterinary Treatment: What Actually Works

Treatment is aimed at removing the placenta safely while controlling inflammation and preventing complications.

1. Oxytocin Therapy

Oxytocin stimulates uterine contractions.

How it is used

• given in small, repeated doses

• encourages the uterus to expel retained tissue

Clinical insight

Smaller, repeated doses are often more effective than large single doses.

2. Uterine Lavage

If oxytocin alone is not sufficient, uterine lavage is performed.

What this involves

• sterile fluid is introduced into the uterus

• fluid helps separate and remove retained tissue

• bacteria and debris are flushed out

This is one of the most effective ways to:

• assist removal

• reduce bacterial load

• limit inflammation

3. Anti-Inflammatories and Supportive Care

These are used to:

• reduce systemic inflammation

• control pain

• lower the risk of laminitis

The specific drugs and protocol depend on the individual case.

Laminitis Prevention: The Critical Step Most People Underestimate

Laminitis is one of the most serious complications associated with retained placenta.

It can develop quickly and may be life-threatening.

Why it happens

Toxins released from the uterus affect blood flow and inflammation in the hoof laminae.

How to Reduce Laminitis Risk

1. Cryotherapy (icing the feet)

Continuous cooling of the feet is one of the most effective preventive measures.

• all four feet should be cooled

• ideally started early if retention persists

• may be continued for 24 to 72 hours

Clinical reality

This is time-intensive, but it can be the difference between preventing laminitis and dealing with a catastrophic outcome.

2. Close monitoring

Watch for:

• increased hoof temperature

• strong or bounding digital pulses

• reluctance to move

• shifting weight

Decision checkpoint

If a mare becomes stiff, reluctant to walk, or stands in a rocked-back position, treat this as urgent.

Severity Framework: How Serious Is the Situation?

Mild

• placenta retained just beyond 3 hours

• mare otherwise bright

Action:
Immediate veterinary involvement still required

Moderate

• retention beyond 6 hours

• early signs of discomfort or inflammation

Action:
Active treatment and monitoring needed

Severe

• prolonged retention

• signs of systemic illness

• uterine discharge

• depression or fever

Action:
Aggressive treatment and laminitis prevention required

Critical

• signs of laminitis

• endotoxemia

• severe depression

Action:
Emergency intensive care

When Is This an Emergency?

This should always be treated as urgent, but immediate emergency care is required if:

• the mare is depressed or not eating

• there is fever

• foul-smelling discharge develops

• signs of colic appear

• lameness or stiffness develops

• digital pulses are strong

• the mare is reluctant to move

These signs indicate systemic involvement.

What Happens After the Placenta Is Removed?

Treatment does not stop once the placenta is passed.

Follow-up care may include:

• ultrasound to check for fluid or retained material

• monitoring for infection

• continued anti-inflammatory therapy

• observation for laminitis

Clinical insight

The biggest mistake is assuming the problem is solved once the placenta is out. The inflammatory cascade may already be underway.

Common Mistakes Owners Make

• waiting longer than 3 hours to act

• pulling on the placenta

• underestimating laminitis risk

• not monitoring after removal

• assuming a small retained piece is harmless

Even small delays can change outcomes.

Prevention: What Reduces Risk?

You cannot prevent all cases, but you can reduce risk by:

• closely monitoring the mare immediately after foaling

• noting the exact time the foal is delivered

• tracking placenta passage carefully

• involving a veterinarian early if there is delay

• ensuring proper postpartum examination

Early recognition is the most powerful preventive tool.

Frequently Asked Questions

Can a retained placenta resolve on its own?

In mares, this is not something to rely on. Intervention is required.

Why is laminitis such a big risk?

Because toxins released from the uterus trigger inflammation in the hoof structures.

Is it safe to cut the placenta if it is dragging?

No. It should be tied up, not cut.

How long does recovery take?

Most mares recover well with prompt treatment, but monitoring continues for several days.

Will this affect future fertility?

It can if infection or uterine damage occurs, which is why early treatment is critical.

Final Thoughts

Retained placenta in mares is not a watch-and-wait condition.

It is a time-sensitive emergency where early action protects the mare from infection, systemic illness, and laminitis.

The key principles are simple:
recognise it early
do not interfere incorrectly
get veterinary treatment quickly
monitor beyond initial resolution

Handled promptly, most mares recover well.
Handled late, the risks increase significantly.

If there is any uncertainty about whether a placenta has fully passed or how a mare is progressing after foaling, ASK A VET™ can help guide immediate next steps and assess urgency with clarity.