According to Midwest Exotic Animal Hospital, common signs of pregnancy in dwarf hamsters include restlessness and bloody discharge prior to delivery. The gestation period for dwarf hamsters is approximately 16 days, with as many as 10 pups per litter.
VCA Animal Hospitals explains that female hamsters are known to fight aggressively with other females when they are pregnant. During breeding periods, females are typically not aggressive toward males. Female hamsters emit a foul-smelling vaginal discharge during ovulation that can be mistaken for a sign of infection.
The ASPCA explains that dwarf hamsters prefer to live in pairs but warns hamster owners against housing male and female hamsters together as they tend to breed rapidly and produce large litters.