Boston terriers are bright, active and intelligent dogs that are popular, ranking in the top 20 most registered breeds with the AKC. Due to their popularity, many Boston terriers are actually bred by their owners. If a female Boston terrier is not spayed, this can happen by accident as quickly as it can happen on purpose. If your dog has been in contact with a unaltered male, look for some key signs of pregnancy.
Monitor your dog's appetite closely if you believe that she's been bred. One of the earliest symptoms of pregnancy is a decreased appetite, though not all dogs experience this.
Watch your dog for lethargy or lack of energy. Pregnancy takes a lot of energy, and may leave your Boston terrier listless and cranky.
Look for nipple growth. Her nipples will begin to get bigger and firmer if she has conceived. The area under the nipples will also swell. This is the most obvious sign of pregnancy, and will be accompanied by an obviously swelling abdomen.
Take your Boston terrier to the vet for confirmation of the pregnancy and a health check. It's important that she be tested for health issues and that her pregnancy is monitored and supported through good nutrition.