According to PetMD, phantom pregnancy in dogs, also known as false pregnancy or pseudopregnancy, is most likely caused by hormonal imbalances, especially of progesterone and prolactin. The female dog starts showing pregn... More » Pets & Animals Animal Reproduction

PetMD lists behavioral changes, nesting, attempting to nurse, enlarged mammary glands, restlessness, lactation and a swollen abdomen as signs that a female dog is affected by a phantom pregnancy. The symptoms vary somewh... More »

Pregnancy and menopause can be causes of a phantom period, according to What to Expect and Menopause A to Z, respectively. A phantom period is when a woman experiences the symptoms of a period with no actual bleeding. More »

While the exact length of the gestation period for a tropical fish varies from species to species, the average pregnancy lasts about one month, give or take a week. More »

Horses reproduce by going through a process which includes fertilization, pregnancy and growth before the cycle starts all over again. Horses also have a hormone cycle that includes several phases to help ready the mare ... More »

Pregnancy signs in dogs vary by term of the pregnancy and may include the dogs not being hungry as often and being exhausted during the early stages, notes WebMD. As the pregnancy progresses to the midterm, the dog might... More »

Facts about horse breeding include that horses breed in the spring and summer, a horse's pregnancy period spans 11 months, light encourages horses to produce reproductive hormones, horses should reach 4 years of age befo... More » Pets & Animals Animal Reproduction