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.
Dogs are normally pregnant for 9 weeks, but this time period can fluctuate by a week before or after the average 63 days of gestation. For larger litters the pregnancy usually lasts less than 9 weeks, while the opposite is true for small litters. Initial signs of pregnancy in the first three weeks include: