Accidental pregnancy is common in dogs. Male dogs are remarkably adept at getting to females in heat. The usual measures, such as confining a female in a run or pen, are not always sufficient to protect her from a determined male.
To be absolutely safe, keep your bitch indoors when she’s in heat; take her out on a leash only. When outside, do not let her out of your sight for even one minute. She should be confined throughout the entire estrous cycle, which begins with the first show of color and continues for at least three weeks.
Chlorophyll tablets, which you can purchase from your veterinarian or at pet supply stores, may help to mask the odor of a female in heat, but are not effective in preventing mating.
If you witness a tie or suspect for any reason that your bitch may have been bred, take her at once to your veterinarian. The stage of the heat cycle can be determined by vaginal cytology and a serum progesterone assay. The bitch may not have been in her fertile period, in which case pregnancy is unlikely. Sperm in the vagina can often be identified during the first 24 hours after mating, but absence of sperm does not rule out breeding or pregnancy.
If it appears that the bitch has indeed been bred and is likely to become pregnant, there are two alternatives: One is to wait and see if she becomes pregnant, then allow her to go through with her pregnancy; the other is to treat for termination, either before or after the pregnancy is confirmed.
The first alternative, allowing the bitch to carry her litter, is the safest and best if she is valuable and you are planning to breed her in the future. However, if she is not of breeding quality and you do not have the time and facilities to raise a litter of puppies and find suitable homes for them all, your best choice is to have her spayed. This can be done during the early stages of pregnancy without added risk. During the second half of pregnancy, hysterectomy becomes more difficult.
There is no uniformly safe and effective medical alternative to spaying for preventing or terminating pregnancy in dogs. Preventing pregnancy using estradiol cyprionate (ECP), the mismate shot, is no longer recommended because of the high risks of estrogen-induced bone marrow suppression and pyometra. In addition, the shot is not reliable, even when given during the required three to five days after breeding.
Terminating pregnancy with prostaglandin PGF2a (Lutalyse), although associated with significant complications including rupture of the uterus and gastrointestinal and respiratory distress, may be the best medical alternative currently available for inducing abortion. There are early and late treatment protocols. The late protocol, with which there has been the most experience, uses ultrasonography or abdominal palpation to diagnose pregnancy at 30 to 35 days after breeding. If the bitch is found to be pregnant, she is hospitalized and given Lutalyse injections daily for four to seven days.
Lutalyse causes the corpora lutea in the ovaries to disappear. The corpora lutea manufacture the progesterone that maintains the pregnancy. Although treatment is successful in the majority of cases, it is important to verify that pregnancy has indeed been terminated by obtaining a follow-up ultrasound and serum progesterone level. And the possible side effects (mentioned above) can be serious.
Early pregnancy termination using Lutalyse uses a similar protocol, but the hormone is given 10 days after breeding, before pregnancy is actually confirmed. The advantage of early treatment is that no dead puppies are aborted. The disadvantage is that some non-pregnant bitches may be subjected to unnecessary treatment.
Several other drugs are available for inducing abortion in bitches. The drug RU-486 is under investigation and may prove to be an effective and relatively safe drug for inducing abortion in the first half of pregnancy. Currently, it is not approved in the United States for use in dogs. A related drug, aglepristone, is being studied in Europe for use as an abortifacient in dogs. Dexamethasone (a cortisone preparation) terminates pregnancy in midgestation, but specific protocols have not yet been established.
The inconvenience of a pregnancy must be weighed against the potential risks and complications associated with terminating the pregnancy. Discuss all these options fully with your veterinarian before making a decision.