Can You Ride a Mare in Early Pregnancy?

By Dr Duncan Houston

One of the most common questions owners ask after breeding a mare is simple: can I still ride her?

The honest answer is: usually yes, but timing matters. A healthy pregnant mare does not automatically need to be wrapped in cotton wool, shut in a stable, and treated like she might explode if she trots. Movement is good for most mares. But the very early pregnancy window is different from the rest of gestation.

The most sensitive period is around ovulation, fertilisation, early embryo development, maternal recognition of pregnancy, and embryo fixation. Heavy exercise, heat stress, dehydration, travel, pain, or hard training during that period may reduce the chance of a successful pregnancy, especially in performance mares or embryo donor mares.

Quick Answer

Many mares can continue light to moderate exercise during pregnancy, but it is sensible to avoid hard work, heat stress, and intense training from breeding through the first pregnancy check. The embryo moves around the uterus until about day 16 after ovulation, and this early period is when pregnancy recognition and early embryo survival are most vulnerable. Research suggests moderate exercise from day 16 to day 80 did not harm pregnancy in a small study, but heavy or heat-associated exercise around ovulation and embryo recovery has been linked with reduced embryo recovery rates. (Merck Veterinary Manual)

Why the First 16 Days Matter

Early pregnancy in mares is unusual compared with many other species. The embryo enters the uterus around day 6 after ovulation, then moves throughout the uterus until around day 16. This movement is part of how the mare recognises that she is pregnant. Merck Veterinary Manual notes that the spherical conceptus moves through the uterine horns and body from day 6 to 16, and the University of Georgia describes days 12 to 14 as critical for maternal recognition before fixation around day 16. (Merck Veterinary Manual)

That means the first two weeks after ovulation are not a great time to add extra stress if pregnancy is the priority.

This does not mean the mare must stand still for 16 days. Quiet turnout, walking, calm handling, and gentle routine are usually fine. The concern is heavy work, overheating, dehydration, intense canter sets, hard competition, long transport, illness, pain, or any management change that makes the mare genuinely stressed.

What Does the Research Say?

There are two different questions here, and they should not be mixed up.

The first question is whether exercise around ovulation and early embryo recovery can affect fertility. In one study, mares exercised daily for 30 minutes in hot and humid conditions had lower embryo recovery than control mares, with embryo recovery reported as 34% in exercised mares compared with 63% in controls. (PubMed)

A related study on moderate exercise and early embryonic outcomes also reported that exercise affected reproductive physiology and early embryo outcomes, with rest after ovulation not clearly improving embryo recovery. (PubMed)

The second question is whether exercise after pregnancy has already been detected is harmful. A small study exercising mares from day 16 to day 80 of gestation found no significant harm to embryonic vesicle size, no difference in uterine blood flow between groups, and all mares delivered healthy foals. Fetal length tended to be longer in the exercised group, but this was a small study and should not be used as permission for hard training in every pregnant mare. (ResearchGate)

The practical takeaway is simple: light to moderate exercise is often safe after pregnancy is confirmed, but the breeding-to-day-16 window deserves more caution.

Is Day 16 a Magic Safe Point?

Not exactly. Day 16 is not a magic switch where risk disappears. It is simply an important biological and management checkpoint.

Around this time:

• The embryo usually becomes fixed in the uterus

• A first pregnancy scan is often performed

• Twins may be detected

• The vet can check whether the mare is pregnant

• The plan can be adjusted if the mare is open

Merck describes one common pregnancy check schedule as scanning around days 14 to 18 to confirm pregnancy and check for twins, then scanning again around days 25 to 30 to assess normal development and heartbeat. (Merck Veterinary Manual)

This is why I would not make big training decisions based only on “she was bred.” I would base the plan on ovulation date, pregnancy scan timing, mare risk factors, weather, workload, and what the owner is trying to achieve.

What Exercise Is Usually Safe?

For a healthy mare with no reproductive concerns, safe exercise usually means calm, controlled, familiar work.

This may include:

• Turnout in a safe paddock

• Hand walking

• Light hacking

• Gentle flatwork

• Walking and easy trotting

• Light schooling in cool weather

• Normal movement without exhaustion

Merck Veterinary Manual states that pregnant mares need adequate daily exercise in a paddock or pasture, and that compatible turnout helps decrease stress. (Merck Veterinary Manual)

So the answer is not “no movement.” The answer is “avoid unnecessary intensity and stress.”

What Exercise Should Be Avoided?

Be more cautious with:

• Hard canter or gallop sets

• High-intensity conditioning

• Jumping large fences

• Fast work in deep or slippery footing

• Hard work in hot or humid weather

• Long-distance transport around ovulation

• Competition during the early pregnancy window

• Work that leaves the mare overheated or exhausted

• Riding a mare that is lame, sore, febrile, colicky, dehydrated, or dull

The biggest multiplier is heat. A workload that is reasonable on a cool morning may become a poor decision in hot, humid weather.

Suggested Exercise Plan by Pregnancy Stage

This is not a rigid rulebook. It is a decision framework. The mare’s health, pregnancy history, weather, workload, and veterinary findings matter more than a calendar alone.

Severity and Risk Framework

Low Risk: Healthy Mare, Light Work, Cool Weather

This mare is bright, sound, in good body condition, not overheating, and doing light work or turnout.

What to do: continue sensible movement, avoid sudden workload increases, and keep routine pregnancy checks.

Medium Risk: Mare in Regular Work During Breeding

This mare is still being ridden, schooled, or lightly trained while being bred.

What to do: reduce intensity around ovulation and the first 16 days after ovulation. Prioritise ultrasound timing and avoid heat stress.

High Risk: Heavy Work, Heat, Travel, or Performance Pressure

This mare is in serious training, competing, travelling, or working hard in hot and humid conditions around breeding.

What to do: treat this as a fertility risk. Reduce workload, shift work to cooler times, prioritise hydration and cooling, and discuss embryo transfer if competition cannot pause.

Critical Risk: Sick, Painful, Overheated, or Pregnant With Warning Signs

This mare is unwell, colicky, lame, feverish, dehydrated, bleeding, discharging, heat stressed, or suspected to be losing the pregnancy.

What to do: stop exercise and call your vet.

What Else Affects Early Pregnancy Success?

Exercise is only one part of the picture. If a mare does not conceive or loses a pregnancy, do not blame riding alone.

Important rule-outs include:

Poor Breeding Timing

Timing matters enormously. The University of Georgia notes that insemination too long after ovulation can contribute to aged-oocyte problems and embryonic loss. (CAES Field Report)

Twins

Twins are a major problem in mares. Early scanning matters because twin management is easiest before fixation. The University of Georgia notes that manual reduction is best performed before day 16 while embryos are still mobile. (CAES Field Report)

Uterine Infection or Endometritis

A uterus with infection or inflammation is a poor place to support early pregnancy. Uterine infection can affect progesterone support and the endometrial environment needed for the conceptus. (CAES Field Report)

Mare Age

Older mares often have lower oocyte quality, poorer uterine clearance, more fluid issues, and higher early pregnancy loss risk. The older maiden performance mare deserves a proper reproductive work-up, not just another breeding attempt.

Semen Quality

Frozen semen, cooled semen, poor handling, delayed insemination, or poor stallion fertility can all affect pregnancy rates.

Progesterone or Luteal Support Problems

Progesterone is important for early pregnancy maintenance. If there is concern about luteal function, repeated pregnancy loss, or abnormal early scans, your vet may discuss testing or treatment.

Stress, Climate and Management Change

The University of Georgia lists stressors such as abnormal exercise, nutrition, climate, palpation, transportation, and herd changes as possible contributors to pregnancy risk in susceptible mares. (CAES Field Report)

The key phrase is “susceptible mares.” One mare may tolerate a management change well. Another mare with previous loss, uterine disease, or poor body condition may not.

When Is This an Emergency?

Call your vet promptly if a pregnant or recently bred mare shows:

• Colic signs

• Fever

• Depression

• Refusing feed

• Severe heat stress

• Laboured breathing after exercise

• Collapse

• Vaginal bleeding

• Abnormal vaginal discharge

• Sudden severe lameness

• Suspected fall or trauma

• Signs of laminitis

• Premature udder development

• Milk leakage well before foaling

• Suspected pregnancy loss

Do not continue riding a mare that seems unwell just because she is “early” in pregnancy. Early does not mean low stakes.

What Should You Do Next?

1. Confirm the Ovulation Date

Exercise decisions are best made from ovulation date, not just breeding date. Ask your vet when the mare ovulated or when ovulation was expected.

2. Keep Work Light Until the First Scan

From breeding through the day 14 to 18 pregnancy scan, keep the mare in a calm, cool, low-stress routine. Turnout and light movement are fine for many mares. Hard training is not worth it if pregnancy is the goal.

3. Scan at the Right Time

A first ultrasound around days 14 to 18 helps confirm pregnancy and check for twins. A second scan around days 25 to 30 helps assess embryo development and heartbeat. (Merck Veterinary Manual)

4. Avoid Heat Stress

Work early morning or evening. Use shade, fans, hosing, electrolytes where appropriate, and proper cool-downs. Do not work a mare hard in heat just to stay on a training schedule.

5. Match Exercise to the Mare

A fit mare already in work may tolerate light to moderate exercise better than an unfit mare suddenly put into work after breeding.

Do not start a new conditioning program because she is pregnant. Maintain sensibly. Do not suddenly intensify.

6. Adjust After Each Pregnancy Check

Use ultrasound findings to guide the plan. A normal day 16 scan is reassuring, but it does not mean you can ignore the day 25 to 30 heartbeat check or the later day 40 to 60 reassessment.

7. Consider Embryo Transfer for Performance Mares

If the mare must remain in hard work or competition, embryo transfer may be the better reproductive strategy. It allows the donor mare to continue her performance career while a recipient mare carries the pregnancy.

8. Stop Work if Anything Changes

Pain, fever, abnormal discharge, colic, marked fatigue, heat stress, or sudden behavioural change should stop the riding plan until the mare is checked.

Common Mistakes Owners Make

Treating Day 16 as Guaranteed Safety

Day 16 is an important checkpoint, not a magic shield. Keep monitoring.

Confusing Light Exercise With Hard Training

Walking, turnout, and light flatwork are not the same as intense conditioning, gallop sets, competition, or hard work in heat.

Ignoring Weather

Heat and humidity change the risk. A mare that copes well in cool weather may overheat quickly in summer.

Skipping the Twin Check

A mare can look completely normal and still carry twins. Early ultrasound is essential.

Blaming Exercise When the Uterus Was the Problem

Uterine fluid, endometritis, poor timing, semen quality, and mare age are often more important than one quiet ride.

Starting a New Fitness Program After Breeding

Pregnancy is not the time to suddenly make an unfit mare athletic. Maintain appropriate movement. Do not push new intensity.

Prevention: A Better Early Pregnancy Exercise Plan

A sensible plan should include:

• Pre-breeding reproductive exam

• Body condition assessment

• Soundness check

• Accurate ovulation timing

• Light work from breeding to first scan

• Avoidance of heat stress

• No hard work around ovulation

• Pregnancy scan at days 14 to 18

• Twin check

• Heartbeat check at days 25 to 30

• Recheck around days 40 to 60

• Clear communication between owner, rider, trainer, and vet

• Embryo transfer discussion if the mare must stay in hard work

The best plan is boring in the right way. No panic, no guesswork, no “she’ll be right” breeding management. Just good timing, sensible exercise, and proper ultrasound monitoring.

FAQ

Can I ride my mare after she has been bred?

Yes, many mares can be lightly ridden after breeding, but I would avoid hard work, heat stress, and intense training until the first pregnancy scan. If pregnancy is the priority, keep the first 16 days calm.

Should I stop all exercise in early pregnancy?

Not usually. Quiet turnout, hand walking, and light exercise are often helpful. Complete stall rest is not needed unless your vet recommends it for a medical reason.

Why is day 16 important in mare pregnancy?

Around day 16, the embryo usually becomes fixed in the uterus. Before that, it moves throughout the uterus and is involved in maternal recognition of pregnancy. This is also around the first pregnancy scan window. (Merck Veterinary Manual)

Is exercise from day 16 to day 80 safe?

A small study found that moderate exercise from day 16 to day 80 was not detrimental to pregnancy, and all mares delivered healthy foals. However, that does not mean every mare should continue hard training. Use the mare’s health, pregnancy history, workload, and veterinary findings to guide the plan. (ResearchGate)

When should I stop riding a pregnant mare?

There is no single date for every mare. Many owners reduce or stop riding as the mare becomes heavier, often later in pregnancy, but the decision depends on her comfort, soundness, size, pregnancy stage, workload, and vet advice. Hard work should be avoided if the mare is uncomfortable, unwell, overheated, lame, or showing pregnancy concerns.

Final Thoughts

A pregnant mare does not need to be treated like glass, but early pregnancy deserves respect.

The safest general approach is to keep exercise light and low-stress from breeding until the first pregnancy scan, avoid hard work and heat stress around ovulation and the first 16 days, then use veterinary checks to guide what she can safely do next.

Movement is good. Fitness can be good. But pushing a mare through heavy work while trying to establish a pregnancy is poor planning.

The goal is not to stop the mare living normally. The goal is to avoid unnecessary stress at the exact time her body is trying to establish and protect a pregnancy.

If your mare has just been bred, is newly confirmed pregnant, or you are unsure whether her current workload is safe, ASK A VET™ can help you work through the timing, risk factors, and when veterinary reproductive support is needed.