Let’s start with the canine heat cycle. The canine heat or estrous cycle varies in length. Many people know that their dog goes into "heat" but don’t realize that unlike the human menstrual cycle, which is a non-fertile stage, dogs that are in heat are preparing to ovulate. There are four stages of the estrous cycle. The first stage is proestrus, which is characterized by increased follicular activity of the ovary, a stage that is necessary prior to the release of the eggs. Outward signs include vulvar swelling and bleeding. During this time, your dog will be attractive to males but not receptive to them. In general, this stage lasts six to 11 days with an average of nine days. The end of this cycle is noted when your pet becomes receptive to the male and will stand to be bred. http://postonfire.com/Pets/types_of_dogs
The second phase is the actual fertile phase or estrus. During this time, the discharge becomes more straw-colored to light pink and the vulva, although still swollen, is softer. The female is now receptive to males and will stand for breeding. This stage generally lasts five to nine days. Unfortunately, it can last as long as 20 days and still be normal. Each dog is different and must be monitored closely. The end of this stage is characterized by the female no longer accepting the male.
The last two stages of the estrous cycle are diestrus, a non-receptive time when the corpora lutea, which produce progesterone, are active on the ovary and anestrus. During anestrus there is no ovarian activity. Diestrus and anestrus are lengthy periods: diestrus lasts 56 to 60 days and anestrus is variable, but several months long. Most dogs cycle twice a year.
The next step in the course of the pregnancy is the actual conception…well, I hope you know how that works, so I’ll skip that part. It takes about 62 days from the day that your dog is bred for the puppies to be born.
If you are told the dog is not pregnant, don’t give up all hope.
It is still a good possibility she is and the doctor just didn’t do the palpation at the correct time.
At a later date, the doctor can do an x-ray to look for skeletons.
This is an excellent method for it gives you a definite answer as to if you have a pregnant dog and it also can tell you how many puppies there are.
This is useful information when the mother decides to give birth in the middle of the night.
Plan on feeding a good quality puppy food from the time of breeding. This will insure the proper nutrients and minerals are available for the healthy development of the puppies.
http://www.alltheinternet.com/texis/open/allglobal?q=http%3A%2F%2Fwww.dogbreedss.org