Unless strictly supervised, dogs mate when the mood strikes and the time is right. Unfortunately, some breedings are not intended and unwanted pregnancies can occur. In veterinary medicine, dealing with undesired matings and resultant unwanted litters has resulted in various methods of early pregnancy termination.

The easiest, safest and most reliable treatment for unwanted litters is to spay the dog. This removes the ovaries and uterus, thereby not allowing the pregnancy to develop. This method is a permanent solution and is obviously only to be used in dogs not intended for breeding.

If a future planned pregnancy is desired, surgery is not an acceptable option. Other medical ways of terminating a pregnancy must be considered.

Diagnosis

The most important aspect of terminating a pregnancy is to confirm that there actually is a pregnancy to terminate. With one breeding, the dog has only a 40 percent chance of actually being pregnant. The drugs used to terminate a pregnancy can have significant side effects so confirming a pregnancy is important. Giving a drug unnecessarily can result in serious illness.

Pregnancy can be confirmed after about 20-22 days after breeding. Abdominal palpation and abdominal ultrasound can diagnose the presence of fetuses. At this point, termination can be done appropriately. It is important to confirm pregnancy as early as possible because if the pregnancy is over 40 days along, termination is not recommended due to the potential trauma of expelling live premature babies.

Unfortunately, due to differences in reproduction between humans and dogs, the "morning after" pill has yet to be thoroughly tested and found to be effective in pets.

Treatment

Several medications have been used to terminate unwanted pregnancies, although no one drug has been found to work in all cases. Your pet may receive medication to terminate a pregnancy and still deliver a litter. Even though many dogs have successfully received these drugs and have had no complications, there is the potential for significant side effects. You may want to discuss allowing the dog to carry the pregnancy to term and deliver the babies in order to avoid the side effects of the medication.

Three primary classes of drugs have been used in pregnancy termination: estrogens, prostaglandins and glucocorticoids.

Estrogens

These drugs work by preventing fertilized eggs from migrating and implanting in the uterus. The only way these drugs work is to give them soon after the unplanned breeding. Pregnancy cannot be confirmed at this stage and by giving this drug, your pet may be susceptible to dangerous side effects unnecessarily. These include:

Bone marrow suppression. This condition results in severe anemia, low white blood cell levels and low platelet counts. It can occur within two weeks to two months after administration of the drug and is typically irreversible and eventually fatal.

Pyometra. This uterine infection is another side effect of estrogen administration. Typically, this infection is not effectively treated with antibiotics and spaying may be required.

Infertility. Although this may occur following administration of estrogens, the exact reason is still unknown.

The most commonly used estrogens are:

Estradiol cypionate (ECP)

Diethylstilbestrol (DES). The injectable form of this drug has recently been removed from the market. The oral form is not effective in terminating pregnancy.

Prostaglandins

In order to maintain a pregnancy, the hormone progesterone is required. This class of drugs works by reducing the levels of progesterone, which results in pregnancy termination. This drug is used after pregnancy has been confirmed. It is possible that your dog will not be sensitive to the prostaglandins and these drugs may not work. It is strongly recommended that your pet be hospitalized during prostaglandin treatment, which may four to seven days. This class of drugs is safer than estrogens and preferred by many veterinarians.

The most serious side effect of prostaglandin administration is the potential for pyometra, a uterine infection. Typically, this infection is not effectively treated with antibiotics and spaying may be required. There have been no reports of infertility associated with administration of prostaglandins.

An adverse effect of prostaglandins is the potential of failure to terminate the pregnancy or to terminate only part of the litter. Abdominal ultrasound is recommended to confirm complete pregnancy termination.

Commonly used prostaglandins to terminate pregnancy are:

Cloprostenol

Lutalyse (PGF)

Glucocorticoids

This class of drugs only works on terminating pregnancies in the late stages of gestation and it not consistently effective. The way these drugs work to terminate a pregnancy is not fully understood. By terminating in the late stages of pregnancy, the aborted babies are typically expelled from the uterus. This can be traumatic for the dog as well as the owner. Temporary side effects associated with glucocorticoids are limited to increased thirst and increased urination after the treatment has ended. The most commonly used drug is dexamethasone.

Home Care and Prevention

There is no home care for undesired matings. Douching after breeding is not effective. The best way to prevent unwanted litters is to have your pet spayed early. If you plan to use the dog for breeding, make sure she is strictly confined when in heat and is not accessible to males.