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.
How Long Yorkies are Pregnant. Canines in general are pregnant for an average of 63 days. However, as few as 58 days and as long as 68 days of pregnancy is considered normal for a toy breed dog. If a Yorkie has not delivered by day 67, it will be time to call the veterinarian. Hannah,4 yrs. old, Day 50 into her pregnancy and doing great!