Pseudopregnancy (phantom pregnancy; false pregnancy; pseudocyesis) is a relatively common phenomenon in small dogs characterized by pregnancy behaviour, physical changes associated with pregnancy, but the absence of foetuses.
Pseudo pregnancy is a normal physiological process that occurs in female dogs, not usually associated with reproductive organ disorders. It is seen 45-60 days after a normal estrous (heat) period, as progesterone levels, which rise after ovulation, begin to fall. Decreasing progesterone leads to an increase of prolactin, responsible for most of the behaviors seen during a pseudopregnancy episode.
Clinical signs include mothering of toys, nesting, or even aggression. Mammary development and milk production are common. Mastitis and vaginal hyperplasia are sometimes observed as a complication. Pseudopregnancy can also be acutely induced by spaying a dog near the end of estrus.
Treatment usually involves hysterectomy or allowing time for symptoms to abate by normal hormonal resolution.
Cabergoline (5 μg/kg - 15 μg/kg) may be indicated if excessive prolactin production is evident (>4 ng/mL).
- Tsutsui T et al (2007) Plasma progesterone and prolactin concentrations in overtly pseudopregnant bitches: a clinical study. Theriogenology 67(5):1032-1038