Dogs are pack animals by nature, and their pack mentality does not dissipate when a female gets pregnant. Many owners assume male dogs should be kept away from expectant females, but this is true only in the last few weeks of pregnancy through weaning.
First Three Weeks
A dog’s gestation period is approximately nine week long. Few changes are noticeable during the first three weeks of pregnancy. Your female may be cranky and growl or snap at your male, but this is common as her hormone levels change. There is no need to separate them unless the bickering turns into aggression.
Second Three Weeks
During the next three weeks of pregnancy, the growing puppies may increase your female’s appetite. This may lead to slight food guarding and she should be fed by herself to prevent a fight. Your female may continue to play and interact with your male, but she should not be allowed to exhaust herself.
Final Three Weeks
Isolate your female from all other dogs during her final three weeks of pregnancy. Isolation reduces the likelihood of communicable disease transmission and allows her to get comfortable in the whelping area. Keep the new mother and puppies away from other dogs until they are 3 weeks old, and introduce the male to the litter only if he is healthy and up-to-date on all vaccinations. If your male is not neutered, keep him away from mom until the litter is weaned. Females can become pregnant while nursing.