Mare Gestation Calculator

How Long Are Horses Pregnant? Understanding Mare Gestation

Horse pregnancy typically lasts between 320-365 days, with an average of 340 days (approximately 11 months). However, gestation length varies by breed, individual mare, and environmental factors.

Key Factors Affecting Mare Gestation Period:

• Breed Differences: Draft horses often have longer pregnancies (up to 365 days), while Arabians may foal earlier (~330 days).

• Season & Daylight: Mares bred in spring tend to have slightly shorter pregnancies than those bred in winter.

• Foal Gender: Studies suggest male foals may gestate 1-2 days longer than females.

• Mare’s Age & Health: Older mares or those with health issues may carry longer.

Mare Gestation Calculator: Estimate Foaling Date

Use our interactive calculator to track your mare’s pregnancy progress in real-time. Simply enter the breeding date and adjust gestation length based on breed.

How to Use This Calculator:

1. Enter Breeding Date – The date your mare was last bred.

2. Select Breed (Optional) – Choose from common breeds with preset gestation lengths.

3. Adjust Gestation Days – Fine-tune if you know your mare’s typical pregnancy length.

4. View Results – See estimated foaling date, current gestation days, and progress.

Horse Pregnancy Timeline: Key Milestones

Signs Your Mare Is Close to Foaling

• Udder Development: Begins 2-6 weeks before birth

• Waxing Teats: Milky droplets form (“waxing”) 24-48 hours pre-foaling

• Relaxed Vulva: Muscles loosen 1-2 weeks before birth

• Restlessness: Pacing, sweating, frequent lying down

Foaling Probability by Gestation Day

• Day 320-330: 5-10% chance (early but possible)

• Day 335-345: 60-70% chance (most common window)

• Day 350+: 20-30% chance (monitor closely)

Veterinary Care During Mare Pregnancy

• Month 1-3: Confirm pregnancy, check for twins

• Month 4-6: Routine checkups, nutrition adjustment

• Month 7-9: Vaccinations (tetanus, EHV-1), deworming

• Final Month: Pre-foaling exam, monitor calcium levels

Always consult with your veterinarian for pregnancy management and foaling preparation.

FAQs About Mare Gestation

Q: Can a mare’s pregnancy go longer than 365 days?

A: Rarely. If gestation exceeds 365 days, consult a vet—prolonged pregnancies risk complications.

Q: What’s the shortest safe gestation for a horse?

A: Foals born before 320 days often have underdeveloped lungs. Survival rates improve after 330 days.

Q: Do mares show pregnancy symptoms early?

A: Not usually. Most show physical changes only after 5-6 months.

Q: How accurate is this gestation calculator?

A: It provides estimates based on averages. Individual mares may vary by ±15 days.

Q. What is the average gestation period for a mare?

The average gestation period is 340 days (11 months), but it can range from 320–370 days depending on breed, season, and individual factors. Draft horses often carry longer (up to 365 days), while Arabians may foal earlier (~330 days).

Q. Can a mare’s gestation period vary?

Yes! Factors like breed, foal gender (males may gestate 3–4 days longer), and season (spring foals often arrive earlier) cause variations. Some mares deliver at 310 days, while others exceed 370 days .

Q. What are the signs a mare is close to foaling?

Key signs include:

• Udder development (2–6 weeks pre-foaling)

• Waxing teats (24–48 hours before birth)

• Relaxed vulva and restlessness

• Nesting behavior (pacing, lying down frequently) .

Q. Can a mare have twins?

While possible, twin pregnancies are high-risk and often result in miscarriage or stillbirth. Vets typically reduce one embryo early via ultrasound (around Day 14–16) .

Q. How early can a foal survive?

Foals born before 320 days are premature and face severe health risks (underdeveloped lungs, weak immunity). Survival improves after 330 days, but intensive neonatal care is critical.

Q. What should I feed a pregnant mare?

• First trimester: Maintain regular diet.

• Third trimester: Increase protein (40% more) and calories to support rapid fetal growth. Avoid fescue hay (linked to prolonged gestation).

Q. When should a mare stop working during pregnancy?

Most mares can work lightly until 8–9 months. Reduce strenuous activity in the final trimester to avoid stress.

Q. How do I confirm pregnancy in a mare?

• Ultrasound at Day 14–16 (checks for twins).

• Heartbeat detection by Day 45.

• Palpation or hormone tests .

Q. Can older mares (20+ years) get pregnant?

Yes, but fertility declines. Mares over 15 may need extra veterinary monitoring for complications like placental issues.

Q. What vaccinations are needed during pregnancy?

• Rhino/Herpesvirus at 5, 7, and 9 months (prevents abortion).

• Tetanus/West Nile in late gestation.

Q. How long after foaling can a mare breed again?

Mares can cycle 7–10 days post-foaling (“foal heat”), but vets often recommend waiting until the second cycle (~30 days) for better uterine recovery.

Q. What causes prolonged gestation (>370 days)?

• Fescue toxicosis (a fungus in hay).

• Delayed fetal development.

• Breed tendencies (e.g., Draft horses).

Q. Is it safe to ride a pregnant mare?

Light riding is generally safe until mid-pregnancy, but avoid risks of falls or stress in late gestation.

Q. How do I prepare for foaling?

• Clean, quiet foaling stall with thick straw bedding.

• Monitor for labor signs (waxing teats, sweating).

• Have vet contact ready for emergencies .

Q. Can mares have false pregnancies?

Yes! Hormonal imbalances may mimic pregnancy symptoms. Always confirm via ultrasound