The Daily Puppy reports that the first stage of dog labor lasts anywhere from 16 to 24 hours. It indicates that the second stage of dog labor can last as long as 12 hours.
Dog labor is typically broken down into two parts, as explained by 2nd Chance. The first stage begins roughly 24 hours before the dog begins active labor. During this stage, the cervix starts dilating and contractions begin. Signs of the first labor stage include a drop in the mother's temperature, restlessness and not eating.
According to 2nd Chance, the second stage of labor occurs when contractions become stronger and actual birth begins. Typically, puppies are birthed every 30 minutes and the overall process can take several hours. After each puppy is born, the mother often cleans the puppy and gets rid of the umbilical cord.