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Take your dog to the veterinarian before she becomes pregnant. Make sure your dog is getting the right kind of nutrition. Prepare for the due date. Have your veterinarian take x-rays of the puppies. Set up a nesting area. Arrange for homes for the puppies. Buy puppy formula ahead of time. Isolate the mother three weeks before expected delivery. Prepare for the actual delivery.
If you expect to breed your dog, take her to the vet beforehand. If your dog becomes pregnant unexpectedly, take her as soon as you become aware of it.  If you plan to breed your dog, it’s recommended that you wait until she’s at least 24 months old, which will allow the dog to fully mature so any medical problems that may affect a pregnancy will become apparent. Small dog breeds may have genetic conditions that are important to be aware of before breeding, including dental problems, dislocating patellas, hip dysplasia, spine problems, allergies, heart conditions, and/or behavioral problems. If your dog has these problems, do not breed her. Make sure that your dog is up to date on vaccines. Her antibodies will be passed on to the puppies through her milk and will help protect the puppies from getting sick. Make sure that your dog is on a deworming program. Roundworms, hookworms, heartworms and others can be passed from a mother to her puppies. Your vet can offer recommendations as to the best food for her during her pregnancy. If your pregnant dog is not obese, your vet may recommend feeding her puppy food in the latter weeks of her pregnancy.  The higher calories in puppy food will help the mother pass on additional nutrition to her growing puppies. Avoid supplements such as calcium unless your veterinarian prescribes them. Milk fever, or eclampsia, is common for small breed dogs a few weeks after giving birth, and it’s more likely to occur with over supplementation of calcium during pregnancy. The average gestation period for a dog is between 58 and 68 days. Calculate the dog's expected due date based on the date of conception, so that you'll be prepared when the time for labor comes. Your pregnant chihuahua is likely to display nesting behaviors and may withdraw from people in the final weeks of her pregnancy. This is normal. At 45 days of pregnancy, the vet will be able to count the number of puppies in the litter using x-rays.  Since a Chihuahua is a small breed dog, 3 or 4 puppies in a litter is plenty. However, if only one or two are seen, that may pose problems at the time of birth. Fewer puppies mean the puppies will be larger and may be too big to pass through the birth canal naturally, so a planned C-section would be best. Though a planned C-section will be more costly, it will still be cheaper than an emergency C-section, so plan ahead. About a week before your dog is due to begin labor, find a quiet area where your chihuahua will be able to give birth in peace. A cozy box or dry paddling pool in a calm and quiet area should do the trick; add old towels or blankets for comfort, and make sure they're clean. As soon as you know your dog’s pregnant, whether it was planned or not, begin arranging for homes for the puppies.  If you aren’t able to find homes for all of the puppies, be prepared to keep them yourself until you can find them a home. Thousands of dogs end up in over-crowded shelters because irresponsible owners breed their dogs without providing homes for the puppies. Don’t be part of the problem. Prepare to live with puppies for a minimum of 8 weeks before they leave your house for new homes. In certain states like California, it’s illegal to adopt out a puppy younger than 8 weeks of age. To ensure the puppies go to good homes, have an application process and ask questions of the interested parties. It’s also recommended that you charge a modest amount for each puppy to ensure the interested parties are serious about and committed to adopting the puppy. Newborn puppies will need to be fed every 2-4 hours around the clock, and if a puppy has trouble nursing, you want to have formula on hand to feed it. You can buy puppy formula at most pet supply stores. To protect the mother and her puppies from contracting illness or disease like canine herpes, confine her away from all other dogs in the three weeks leading up to her expected delivery date. It’s also highly advisable to keep the mother away from other dogs for three weeks following the delivery. When the time comes, help your chihuahua through their labor. You can find a detailed guide specifically on labour at How to Help Your Chihuahua During Labor.