The gestation period for dogs is roughly 63 days. However, a dog pregnancy can range from 58 to 68 days in length. Dog pregnancies are broken down into trimesters; each trimester lasts around 21 days.
The early stages of pregnancy in dogs are often undetectable aside from a few signs, such as loss of appetite, fatigue and slight weight gain. Certain dogs may also experience morning sickness a few weeks into the pregnancy. Veterinarians can determine pregnancy in dogs at around three weeks into the gestation period with an ultrasound. Later signs of pregnancy, such as enlarged nipples and milky discharge, occur around day 40 of the gestation period.
When in labor, the abdominal contractions will commence with the first pup delivered 1 to 2 hours after the contractions have commenced.