* Breed: Some breeds are known for having larger litters than others.
* Age and health of the sow: Younger sows tend to have smaller litters than older sows.
* Nutrition and environment: Proper nutrition and a comfortable environment can lead to larger litters.
* Parity: The number of times a sow has given birth. Sows that have had more litters may have smaller litters.
It's important to note that a sow can have up to 20 piglets in a single litter, though this is not common.