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.
Give puppies safe chews made for puppies. Puppies even as young as 7 weeks old want to chew. Their puppy teeth begin to erupt at 3 weeks of age, and by 6 to 8 weeks, they have all their baby teeth. At 7 weeks old, puppies are still in the litter and learning to chew with their littermates.