Mismating

December, 2000


Occasionally, even a careful dog owner has to deal with an unwanted pregnancy. A male dog’s persistence getting to a bitch in heat can overcome our best efforts to prevent an unintentional breeding.
Several options exist for dealing with this problem. If its not imperative to use this particular bitch for future breedings or she’s getting older and would only be bred one more time anyway, then spaying early in pregnancy is a low risk procedure. Another option that is usually safe for the bitch is to allow her to go through a normal pregnancy and whelping, finding homes for the puppies, even if they’re mongrels.
A third option, chosen frequently, is to call on your veterinarian to terminate the pregnancy safely and effectively. Unfortunately, a perfectly safe means of aborting a pregnancy does not exist. The most common method used to accomplish early abortion involves the administration of high doses of estrogen. This is the hormone that naturally predominates in the female’s body during a normal heat. Just before ovulation, estrogen normally decreases and progesterone becomes the predominant hormone. Progesterone is required to maintain a healthy pregnancy. Giving estrogen by injection or pills can extend the heat period and end the pregnancy. In order to be effective, it must be given within 5 days of breeding. The two common forms of estrogen used by veterinarians are estradiol cypionate, or ECP, and diethylstilbestrol or DES. Side effects are less common with DES, but the drug can be difficult to obtain.
Several serious side effects are possible with the use of estrogen. It can suppress the bone marrow’s production of red blood cells. Rarely, this results in a severe, prolonged or permanent anemia that leads to death. A more likely, but still rare, side effect is pyometra, bacterial infection of the uterus, This is also life-threatening and does not respond to antibiotics alone. Most dogs with pyometra will respond to injections of the hormone prostaglandin (Lutalyse), but the infection is expected to recur after future heats unless the bitch becomes pregnant. Most dogs that develop pyometra are simply spayed
Other drugs have been used to induce abortions in early, middle, and late pregnancy Prostaglandin injections given every day for 4-11 days are about 80 percent effective and nearly always cause gastrointestinal side effects. The longterm effects on the dog’s fertility are not fully understood Dexamethasone, a common corticosteriod given daily can also reliably terminate a pregnancy, but is also not considered safe enough to recommend its use.
In conclusion, there is no perfectly safe method of terminating a pregnancy after mismating has occurred . As is usually the case, the best treatment is prevention .The real solution is better management of the bitch in heat to avoid unintentional breeding, in the first place. Estrogen administration is an effective means of early abortion, and the side effects are rare. But when they occur, they can be life threatening When faced with the problem of an unwanted pregnancy, a thorough discussion with your veterinarian is recommended.


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