According to the ASPCA, there are more than 72 million dogs in American homes. When cats are added into the equation, there are some 100 million pets in America. The demand for pets as family members is met only by breeding. Pet litters determine the availability of some of America's favorite dog and cat breeds. Whether your household pet has an unplanned litter on the way or you are an aspiring breeder, there are some quick facts you need to know about pet litter sizes.
 
Normal litters

There is no conventional litter size for all dog breeds. Different breeds will have different size litters. Generally speaking, smaller dog breeds will produce smaller litters and larger dogs, larger litters. However, there is no set number that is considered normal in any dog breed. Normal is determined by the health of the mother throughout the pregnancy and the development of the puppies in the uterus. A healthy mother with a good diet and steady weight is considered normal.
 
Cats, because there is less variation in physical size between breeds, tend to have smaller litters across the board. Again though, normal will be determined by factors such as healthy weight, good diet, and proper development in the growing kittens.
 
What factors impact litter size? In both dogs and cats, the health and age of the mother will serve as the biggest determining factor in the size of the litter. Older and younger females tend to have smaller litters, as do mothers who are pregnant for the first time. Dogs and cats between the ages of three and five tend to produce the largest litters. Likewise, dogs and cats that maintain a healthy weight are more likely to produce larger litters than obese animals.
 
Complications from large litters

Some breeders will purposely work to try and increase the size of a litter. The most common approach to increasing litter sizes is artificial insemination when eggs are fully mature, but there is little evidence to suggest that this approach works the majority of the time. Regardless, large litters are not uncommon in both dogs and cats. Just like humans giving birth to twins or triplets, there are complications that can arise from large litters in dogs and cats.
 
During labor a mother can suffer from a number of complications that puts the life of mom and newborns at risk. Giving birth to multiples is exhausting and can result in uterine contractions slowing or stopping altogether. With each new puppy or kitten the risk of bleeding increases. The dangers don't end when labor is over either. All those new puppies and kittens need to be nursed. Large litters put mothers at risk of dehydration and exhaustion simply trying to feed so many mouths. The newborns can also be exposed to risk factors such as malnutrition and improper growth patterns as a result.
 
Unique circumstances

Every now and again, there are litters reported that leave people shaking their heads. The American Kennel Club has identified the Labrador Retriever as having the largest litter on average, with 7.6 puppies per litter, but the reality is, any dog is capable of giving birth to as few as one puppy or as many as 20. The Guinness World Record for largest litter size belongs to a Neapolitan Mastiff from England which gave birth to 24 puppies in one litter.