Though there are numerous dog breeds in the world, domestic dogs all share a common reproduction process. Female dogs, or bitches, usually come into heat twice a year and it is during these phases that they can become pregnant. Different breeds of dogs, however, experience different lengths of fertility. When in heat, the female pit bull's fertility lasts 21 days. Pit bulls come into heat for the first time when they are around 6 months old.
Conception through Week Four
Once the fertile female pit bull has mated with a male, you will need to rely on outward symptoms rather than a pregnancy test to determine if she has conceived. Noticing symptoms, however, may take a while, since the first changes are internal and very tiny. The fertilized eggs implant themselves on the wall of the dog's uterus on day 10 or 11. By day 14 or 15 you may be able to detect the pregnancy externally, as your dog's nipples could appear larger and turn a dark pink. In the third week of pregnancy, you may notice your dog going through a sort of "morning sickness." At this stage, the dog might vomit or experience mood swings. She may also appear hungrier at this time. By the fourth week, the puppies' heartbeats should be detectable.
Weeks Five and Six
By week five, you should be able to feel the puppies bodies through the mother's stomach, and her swollen abdomen is another confirmation that you have a pregnant dog on your hands. At this time, an ultrasound can detect the number of puppies. Internally, the puppies are developing into males and females and have developed sufficiently to be recognizable as dogs. The mother may begin to become uncomfortable, appreciating a number of smaller meals rather than one larger one. She may also begin to search for a good spot to deliver her babies and spend more time grooming herself.
Weeks Seven and Eight
By this stage, you can feel the puppies moving inside their mother, if you place your hand on her belly. If you have noticed her searching for a place to give birth, set up a warm, cozy box in a place to which she seems drawn. Once you have placed a box for her to give birth in, allow her to create a comfortable nest there, moving and rearranging the bedding as she wishes. Don't be alarmed if your dog loses interest in food around the eighth week, as her belly might feel so crowded that there doesn't seem to be room for food. Inside the mother, the puppies now have their fur.
Week Nine and Birth
Puppies don't arrive on an exact timetable, but somewhere between 54 and 72 days, roughly 7 and a half to 10 weeks after conception. The average gestation period is just about 9 weeks. For the final week or so, a dog that is ready to deliver might present a clue. If you squeeze her nipples, they might leak a milky fluid or her vagina could emit a discharge. If either symptom appears, you should begin to take a rectal temperature daily. The temperature will indicate when the puppies are ready to be born as it will drop from a normal range of 99 to 101 to a temperature of 97 to 98. This drop indicates an imminent labor and birth, within 12 to 24 hours.