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.

The Third Trimester

The beginning of the third trimester (around day 45) is when you can start to see the puppies on an X-ray (radiograph). Your vet will be able to see how many puppies your dog is carrying, and they'll also ensure that the puppies' heads will pass safely through the birth canal. This is mostly a concern with brachycephalic dog breeds, who may have birth canals that are too narrow to pass big puppy heads. If your vet determines that the puppies are too big to pass safely through the birth canal, then your dog will need to have a cesarean section, or C-section, to remove the puppies when she's done gestating.

Your dog's pregnant belly will also become larger during the third trimester, and it may sway gently back and forth beneath her as she walks. Her mammary chain will swell, and she may leak milk from her nipples. Your dog will likely have a bigger appetite than usual, one that then slows down as she gets closer to delivery. And you may feel and see the puppies moving during the last two weeks of pregnancy.

As your dog's time approaches, she'll likely start looking for and preparing her birthing nest. This can be as simple as a cardboard box or a dog bed with sides that are high enough to keep the puppies inside when mom needs to leave for a break. She may also drag blankets into her nest and arrange them just so. Let her do what she needs to do — just make sure the birthing and nesting area is in a temperature-controlled environment between 85 and 90 degrees Fahrenheit for the first few days.

Make sure to have your vet on speed dial during the last few weeks of pregnancy, just in case anything goes wrong, or if you need help or advice. If your dog doesn't go into labor on the 65-day due date, or if she shows signs of dystocia (difficulty giving birth), then call your vet immediately.

Most of the time, momma dogs instinctively know how to be pregnant, deliver puppies, nurse them and care for them until weaning. Sometimes, however, dogs need our help, which is why knowing how long dogs are pregnant and what to expect can help ensure your dog's pregnancy is safe and joyous.

Dr. Sarah Wooten Dr. Sarah Wooten

Dr. Sarah Wooten graduated from UC Davis School of Veterinary Medicine in 2002. A member of the American Society of Veterinary Journalists, Dr. Wooten divides her professional time between small animal practice in Greeley, Colorado, public speaking on associate issues, leadership, and client communication, and writing. She enjoys camping with her family, skiing, SCUBA, and participating in triathlons.

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