If you're wondering, "How long are dogs pregnant?" read on to learn about the different timeframes and length of pregnancy in dogs.
A normal dog gestation period (or pregnancy) is 63 to 65 days, regardless of the size or breed of the dog. For example, a Chihuahua is pregnant for the same amount of time as a Rottweiler. Though how long dogs are pregnant is shorter than humans, like humans, dogs also have three trimesters. Each one lasts about 21 days. If you think or know your dog has been bred, write down the date so that your veterinarian can have confidence in your dog's due date. Here's what you can expect when your dog is expecting.
The First Trimester
During the first trimester of your dog's gestation period, her appearance won't usually change, aside from gaining a small amount of weight.
A few dogs may develop signs of morning sickness during week three or four, but it's usually not as severe as in humans, and you may not notice anything at all. If your dog throws up once or twice, seems tired and has less of an appetite during this time, don't worry. Offer her a few small meals during the day to ease nausea. If you're worried about your dog, or if her nausea and lack of appetite continue for more than a few days, consult your veterinarian.

Even if your dog seems fine, you should make an appointment with your vet if you think your dog is pregnant. Schedule a prenatal checkup during the first trimester and let your veterinarian know the date that your dog was bred. This is a great chance to ask your vet questions, including what you should feed a pregnant dog. It's best to give your dog a complete and balanced food that's formulated for pregnant or nursing dogs. Your vet may also test for parasites or recommend other tests at this time, including checking hormone levels and/or administering an ultrasound of the fetuses. The ultrasound is a safe and noninvasive way to evaluate the puppies' health.
The Second Trimester
When do you start noticing changes in your pregnant dog's appearance? The second trimester may be when your dog actually starts to look pregnant and gain weight. Her nipples along the mammary chain (the glands along the left or right side of her body) will start to enlarge and may darken in preparation for all the milk they'll need to deliver to the puppies. Not much else happens during the second trimester: Your dog can continue her normal exercise and routine.