The more babies a woman is carrying, the more likely it is that her uterus will swell, triggering contractions, says Brian Brost, M.D., associate professor of maternal/fetal medicine at the Mayo Clinic, in Rochester, Minnesota. An early due date isn't the only challenge to having multiples.
Dogs do not menstruate like humans do. Instead, they come into estrus (come into heat/season) about twice a year, once they have reached sexual maturity. This can sometimes be associated with a small amount of blood from the vulva, but it is not truly a period. Female puppies can reach sexual maturity potentially as early as six months old, although the first season (which is the closest equivalent to getting their period) is often at about nine months old.
Dogs will have their first estrus cycle when they reach puberty. Estrus is the stage of the reproductive cycle in which the dog can become pregnant; sometimes a dog that is in estrus is said to be in heat or in season.On average, puberty or sexual maturity is reached at about 6 months of age, but this can vary by breed.regnancy lasts approximately 9 weeks (63 days) in the dog. However, it is not possible to detect pregnancy during the first 3 weeks. An experienced veterinarian may be able to palpate or feel the fetuses in the uterus of a relaxed dog at about 28-32 days of pregnancy.