I'm to lazy to explain it myself, so I decided to look it up and I will copy and paste the information from this site:http://www.pets.ca/articles/article-dogpregnant.htm Here: A doggie biscuit in the oven The next logical question is, "How can you tell if your dog is in the family way?" Confirming pregnancy necessitates a trip to the veterinary office. The earliest method of pregnancy detection is ultrasound—a nice test because it is noninvasive and very reliable. Fetal heartbeats can be detected at around the 25th day from first breeding. This is not, however, considered a reliable way to determine fetal number. One interesting fact about the canine reproductive cycle is that the dog goes through roughly the same hormonal changes whether or not she is pregnant. For this reason, there is no progesterone blood or urine test to diagnose pregnancy in dogs. There is, however, a blood test that will detect relaxin, a hormone that is produced in pregnant dogs but is not found in non-pregnant dogs. This test may be performed mid gestation, which occurs at around the same time that your veterinarian can palpate the fetuses. Most experienced veterinarians can determine pregnancy by simply feeling the dog’s abdomen during a certain a window of time—about 20-30 days after conception. During this time period, there is uterine swelling around the placental sites that feels like firm and discrete lumps. After 30 days, the uterine swelling is more diffuse and it is difficult to distinguish the gravid uterus from the feel of the intestinal tract. Dogs that are very large or obese may be difficult to examine in any stage, however. A third way to detect pregnancy is by taking x-rays. Fetal skeletons can be visualized at about 45 days of pregnancy. This test cannot be done until late in gestation, but it is nice to know about how many of the little creatures you can expect once the actual birthing occurs. From: http://www.pets.ca/articles/article-dogpregnant.htm

Her tummy gets big and puppies shoot out

does she smell and drop blood once and a while if so yes if it doesn't and you still think your dog is go to the vet and take pictures

obviously his or her stomach will get bigger and bigger so duhh thats how u know if ur fucken dog is prego duhh fucken idiots......its only obvious son unus idiotas pendejos!!!!!!!!