Key facts
- Average length: 340 days
- Normal range: 320 to 360 days
- Heat cycle: about every 21 days
Mares that foal in spring tend to carry longer than those foaling in fall, and mares carrying colts often go a few days longer. Each mare tends to repeat her own gestation length from one pregnancy to the next, so records from previous foalings help narrow the estimate.
Mares cycle about every 21 days. After foaling, the so-called "foal heat" appears 7 to 10 days postpartum.
Frequently asked questions
How many months is a horse pregnant?
About 11 months (340 days on average), with a normal range of 320 to 360 days.
How long is a donkey pregnant?
Longer than a mare: about 12 months (around 365 days, with a range of 350 to 380).