Caring for a pregnant dog has many challenges, but in the end, it is all worth the extra effort.
Hopefully, you were able to get your dog examined by a veterinarian and updated all vaccinations before the pregnancy so protection against many diseases won't be passed down to the puppies. Intestinal parasites can also get passed down from mom to the puppies so it is very important to have your dog checked for these and dewormed if any are present before the pregnancy. Monthly heartworm preventatives should be continued during the pregnancy. This will protect the mom against heartworms and some other parasites. It is very important to prevent fleas and ticks from spreading disease to your pregnant dog, but none of the topical preventatives are recommended to be used on pregnant pets. However, you can use premise sprays in the home and yard to control fleas and ticks. Make sure there is an insect growth regulator (IGR) like methoprene in the product so an infestation in the home can be prevented. Once mom has given birth, you can start to apply the topical product on her again. It is not recommended to apply anything to the newborn puppies, but by protecting mom and the environment, you will help protect them.
Pregnant dogs only need more nutrition and calories in the later trimester and especially during the nursing stage. The biggest mistake you can make is over feeding your pregnant dog. It is important that she does not get fat, but does get the extra nutrients. However, once the puppies are born, let the new mom eat as much as she wants to because it takes a lot of energy to produce enough milk for all of the puppies. It is a good idea to start switching the diet over to a good puppy food, but do it slowly so the soon-to-be mom wont develop any stomach problems from the extra protein and fat puppy food supplies. Start switching the diet over in the last 2 weeks before the impending birth. Always have fresh water available at all times. It is very important that the pregnant mom stay well-hydrated and offering fresh water can help prevent dehydration from happening.
You should notice an increased appetite later during the pregnancy, but it will probably decrease right before giving birth. If you start taking the soon-to-be moms rectal temperature, you should see a decrease by one degree right before giving birth. So if your dogs normal body temperature is 101 degrees, it may fall to 100 degrees. When it does, birthing should take place within 24 hours. That is usually the time the appetite falls and your dog may not want to eat at all that day.
Make sure the diet your pregnant dog is on is a good one. And though you may think it is wise to supplement your pregnant dog with extra vitamins and minerals like calcium, this is not only not recommended, but can actually increase the chances of birthing complications. Once the puppies are born, supplements may be needed, but this should be discussed with your veterinarian.
Schedule a vet visit 4-5 weeks into the pregnancy so mom can be examined and an ultrasound be done to make sure mom and all the puppies are Healthy and Happy.