The Truth About False Pregnancies
As Lorna Boydston's Great Dane approached her due date, she gave every indication that a big litter was on the way.
D. Caroline Coile, Ph.D. |
Posted: Tue Nov 2 00:00:00 PST 2004
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Progesterone levels initially increase, then later decrease during diestrus in the same pattern in both pregnant and non-pregnant females. Elevated progesterone levels are necessary for mammary enlargement, but it is the prolactin that stimulates milk production. Prolactin normally rises during late diestrus in pregnant, and to a lesser extent, non-pregnant bitches. This rise occurs along with the decrease in progesterone, and some evidence suggests that a faster than normal drop in progesterone may cause increased levels or sensitivity to prolactin, thus bringing on lactation in non-pregnant bitches. That may be why spaying a bitch (which causes a precipitous drop in progesterone) during diestrus often (but not always) brings on pseudopregnancy within several days. In fact, the bitches that are more likely to develop pseudopregnancy after spaying during diestrus are usually those that already have a history of pseudopregnancy, suggesting that some bitches are more sensitive to the effect of decreasing progesterone levels.
Pseudopregnancies seldom cause harm, but they can occasionally lead to mammary discomfort or even mastitis, and recurring pseudopregnancies have been linked to subsequent mammary tumor development. Mostly, they are considered a nuisance. They interfere with a bitch's show or performance career. They can cause high stress levels and aggressive behavior. Although most cases will run their course in two to four weeks, many owners seek ways to make the signs go away.
It may be possible to treat symptomatically. If she is continuously licking or nursing from her own mammary glands, a T-shirt, belly wrap, or Elizabethan collar may thwart her. The continued stimulation of the glands will otherwise tend to encourage further milk production, which is why applying compresses or "milking out" the glands is usually counterproductive.
If her problems are behavioral, giving her a mild tranquilizer may do the trick. It's important that the tranquilizer not be from the phenotiazine family, which includes the popular tranquilizer acepromazine. Drugs from this family stimulate prolactin secretion, and thus increase milk production and other symptoms.
Because few therapies are widely available, breeders often resort to using natural remedies such as peppermint. Some report good results; others don't.
The most widely used veterinary therapies have traditionally been based on sex hormones; unfortunately, their side effects usually outweigh their benefits. Estrogens, such as diethylstilbestrol, are not recommended because they can cause uterine disease. Progestins, such as megestrol acetate, can also predispose to pyometra and mammary tumors; in addition, as soon as treatment is stopped the signs are likely to reappear. They are likewise not recommended. Androgens, such as testosterone or mibolerone, can alleviate signs of pseudopregnancy, but they are difficult to obtain.
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