If your dog is expecting, you're eager to know how many puppies will arrive. Your vet can give you an almost definitive answer about six weeks into your dog's approximately eight-week gestation. You can "guesstimate" the number of puppies beforehand by considering various factors, including your dog's size, age and prior breeding history.
Large Breeds and Small Breeds
The smaller the breed, the smaller the litter, and vice versa. Labrador retrievers average 7.6 puppies per litter, while Chihuahuas generally have less than four pups, according to the American Kennel Club. The average number of puppies for an American cocker spaniel was five, while German shepherds averaged six. A 2007 Norwegian Kennel Club study covering more than 10,000 litters from 224 different breeds concluded that "mean litter size increased with breed size, from 3.5 puppies in miniature breeds to 7.1 puppies in giant breeds."
Mating Frequency and Methods
If a dog is bred just once during her heat cycle, she's likely to have fewer pups than if bred several times. Larger litters also occur if the dog is bred at the exact time she's ovulating. Dogs bred naturally tend to have larger litters than those bred via artificial insemination, especially if frozen, rather than fresh, semen is used.
Age of Mothers
The age of the mother and the number of pregnancies she's had affects litter size, no matter what the breed. Both old and young females -- especially in a first pregnancy -- produce smaller litters. While dogs in their prime tend to produce larger litters, that's not true if it's the initial pregnancy. For dogs bred regularly, litter size tends to increase with each pregnancy through about the fourth, with subsequent litters becoming smaller. Once a dog passes the age of 5, litter sizes tend to decrease, except in small breed canines.
Dogs in poor physical condition at the time of pregnancy usually have smaller litters. The same is true of obese canines. Dietary considerations also have an effect, although not the one you might suspect. Dogs fed a good quality commercial food during pregnancy tend to have an average-sized litter based on breed and other factors. There's a reason your vet likely will advise you to avoid feeding your pregnant dog high protein supplements. That extra protein can reduce the number of puppies in the litter.
About four weeks into the pregnancy, your vet can estimate the number of puppies via palpation of your dog's abdomen. At that stage, a vet can feel distinct gestational sacs in the uterus, although she can, at best, give an estimate. As the uterus grows, it becomes more difficult to feel each individual sac. An ultrasound isn't particularly accurate at litter size determination, but an X-ray of the uterus after day 45 can provide you with that information. The fetuses' skeletons mineralize by that time. The Academy of Veterinary Imaging states that radiography proves 93 percent accurate in predicting litter size. That 7 percent inaccuracy rate is attributed to an underexposed X-ray or an undermineralized skeleton.