How long are dogs pregnant?
Canine estrous cycle
Dogs typically have one to two estrous, or heat, cycles per year when they can potentially become pregnant, which means they can have only two litters per year. Dogs are multiparous, which means they can have multiple offspring at once, as opposed to larger animals, such as horses and cattle, whose pregnancy typically yields only one offspring.
Canine pregnancy stages
Canine pregnancy is divided into three equal stages, or trimesters, that last approximately 21 days. During each three-week period, growing puppies reach predictable developmental milestones.
- First trimester — Pregnancy begins when sperm fertilize mature eggs. During mating, sperm are transferred from the male to the female reproductive system, and travel to the oviducts. When eggs are released from the ovary and travel to the oviduct, a single sperm penetrates and fertilizes each egg. The resulting embryos advance to the uterus, where they attach to the uterine lining. The canine uterus is Y-shaped, with two uterine horns leading the uterine body. The embryos implant in the uterine horns, or arms of the Y, and several membrane layers develop around each embryo to form the placenta.
- Second trimester — During the second trimester, fetal tissues differentiate into separate structures and organs. Legs and paws begin to form. Tiny eyeballs develop, each with a rudimentary cornea, lens, and retina. The skeleton forms, as well as organs such as the kidneys, liver, and brain. By the end of the sixth week, at 42 days, each fetus looks like a tiny, distinct puppy.
- Third trimester — During weeks seven through nine, fetal skeletons continue to mineralize, and final details develop. Claws grow, and fine hair that will thicken into a short coat before birth forms over the body. The most important goal of the third trimester is overall fetal growth.
During your dog’s first trimester, you may not observe any external changes. Significant weight gain is not yet expected, and your dog can continue to eat and exercise normally.
During your dog’s second trimester, you may start to notice weight gain, and she may be hungrier. You should change your dog’s diet to a high-quality puppy food to provide more calories, and allow her to eat as much as she likes. You can still take your dog for a daily walk, but limit playtime and avoid roughhousing.
Your dog will continue to gain weight during her third trimester, and you should continue to provide free access to puppy food. She can continue non-strenuous exercise, such as walking, but may not have much extra energy. Toward the end of your dog’s pregnancy, you may notice enlarged mammary glands and nipples as she begins to produce milk. She will begin nesting, or preparing a cozy birthing spot, as the big day approaches.
Canine pregnancy diagnosis
Your family veterinarian can confirm your dog’s pregnancy multiple ways, and she may be able to count the number of puppies you can expect. Pregnancy detection methods include:
- Blood testing — At 20 days of pregnancy, a small blood sample can be tested for the presence of relaxin, a hormone made by the developing placenta. A positive test confirms your dog is carrying puppies.
- Ultrasound — After approximately 24 days of pregnancy, embryos can be detected by ultrasound. Your veterinarian can scan your dog’s abdomen with an ultrasound probe to visualize individual embryos and check for fetal heartbeats to ensure each is viable.
- X-rays — Once fetuses develop mineralized bones, which occurs around 42 days, they can be seen on an X-ray. Although radiation is used to take X-rays, the small amount your dog is exposed to for a single X-ray will not harm her or the puppies. An X-ray allows your veterinarian to see your dog’s entire abdomen in one field, and to count the number of puppies she is carrying. When the time comes for your dog to deliver, knowing the litter size is important, so you can confirm that she has delivered all her puppies, and none remain inside her uterus.
Recognizing whelping signs
As your dog prepares to give birth, you can prepare, as well. Knowing when to expect puppies is important, and you can look to your dog for clues. Ways to pinpoint her delivery date include:
- Counting the days since mating — If you know when your dog mated, you can map out her due date on the calendar by counting ahead 63 days. Keep in mind that this is an estimate, and a normal pregnancy can last from 56 to 70 days. If your dog goes past her expected due date, you should have her examined by your veterinarian to ensure her pregnancy is progressing normally.
- Watching for nesting behaviors — You should set up a comfortable spot for your dog to deliver her puppies. A large box or basket lined with blankets works well for small and medium-sized dogs, but you may need to use a room corner for larger breeds. Puppy pads or other water-proof absorbent materials can be layered under blankets to protect your carpet. As your dog’s delivery date approaches, she will begin to spend more time in this spot. If you do not provide her with a nest, she will make one herself with blankets and other items she finds in your home.
- Monitoring your dog’s body temperature — Canine body temperature often drops one to two degrees fahrenheit prior to whelping, or giving birth. If your dog allows, start taking her rectal temperature daily with a digital thermometer about a week before her projected due date. A sudden drop in body temperature is usually indicates she will give birth in the next 24 hours.
Delivery of puppies
Most dogs deliver puppies on their own without complications, so your dog likely won’t need your help. Regardless, make sure you speak with your veterinarian early on in the process.
Stay nearby in case something goes wrong, but give your dog her space to avoid making her anxious. Puppies should be delivered within 60 minutes of one another. If your dog is straining to deliver a puppy for longer than 60 minutes, she may be experiencing a dystocia, or difficult birth, and you should contact your veterinarian immediately for advice. Your dog should remove the membranes surrounding each puppy and bite through each umbilical cord immediately after a puppy is born, but if she fails to do so, you may need to step in and help.