Dog pregnancies are considerably shorter than human pregnancies -- the period between ovulation and delivery can be less than two months long. Knowing what to expect is critical throughout the gestation period, so that you can be prepared for the delivery. If you aren't sure how far along your dog is, a trip to the vet may be able to provide you with a rough estimate.
The first few weeks of pregnancy are relatively uneventful, though your dog may gain a small amount of weight, appear lethargic and even suffer morning sickness for a few days around weeks three and four. If you suspect that your dog may be pregnant, your vet can perform a blood test to check around day 28 or 30. Then, around day 40, you'll notice her belly and nipples grow. Between days 45 and 49, you may even start to see the puppies moving inside her. Her water will break and she'll start delivering the puppies between days 56 and 66 -- the average length of a pregnancy is 63 days.