How can you tell if your dog has a false pregnancy?

The instinct in dogs is very strong to reproduce. After a female comes into "season", she will often show signs of pregnancy even if not mated, due to this strong influence on her physical system. They can show an enlarged abdomen or uterus, swollen mammary glands, behavior changes such as digging a den, increase in appetite, irritation or aggression to males, and some even produce milk.