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 may not show any signs of pregnancy in the first 2-3 weeks (which is the first third of the pregnancy). Her appetite should remain normal. Pregnant female dogs absolutely do suffer from morning sickness like people do, however not until approximately day 21 after being mated. It usually lasts 1-2 weeks.