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.
A dog's pregnancy lasts, on an average, 63 days. It would be hard to say when your dog will show. Each dog is different, just like each person. The best thing to do, is take her to the vet when you think she would be about half way through the pregnancy and have an ultrasound done. So, about 30 days from the day she was bred, she should go.