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 female dog can only become pregnant when she is breed at the right time, conditions and heat cycle. The duration of pregnancy is usually last about 60 days however this number is only approximation and the real period duration can be shorter or last longer depend on the surrounding conditions and other factors.