In medicine, etiology refers to the many factors coming together to cause an illness. It is normally the focus of epidemiological studies. The etiology of scurvy is a good example. With scurvy, sailors going to sea often lacked fresh vegetables.
So, how long are dogs pregnant? The answer varies depending on several factors, but the average length of gestation, aka pregnancy, lasts between 58 to 67 days, with 63 days being the average delivery date.
Like people, dogs are pregnant for three trimesters, each about 21 days long. Here are a few ways to tell if your dog is pregnant: Early Signs. In the first few weeks, there are very few outward signs, so you may not notice a change. Your dog will seem like her normal self, although she may gain some weight.