Dog: Mismating

Other common/scientific names: unplanned pregnancy, pregnancy termination, abortion

General Information

Mismating or unplanned pregnancies are very common in female dogs. Even the most conscientious owner may have difficulty preventing a canine pregnancy. Female dogs can escape from a yard or kennel in search of a male. Male dogs will break into the yard or stand vigil outside your door when your female is in heat.

A female dog has an estrous (heat) cycle every six to eight months. When a male dog breeds a female dog, a special gland in his penis swells inside the bitch’s vagina. During this time, the male and female are locked together and the male cannot withdraw his penis. This is commonly called a “tie”. Sperm are released at the beginning of the tie which lasts 20-30 minutes. Once a tie is established, the female is at risk for becoming pregnant. The male and female should not be disturbed during this time or injury to the reproductive organs could result.

If your female dog has been bred accidently, call your veterinarian immediately to discuss the options for terminating the pregnancy which are:

  • Mismating injection: An injection of estrogen which had to be given within 72 hours of breeding. No longer recommended because it can cause a life-threatening infection of the uterus called Pyometra.
  • Medical abortion: Hormones and other medications are used. May require multiple injections and hospitalization. Should monitor with ultrasound to confirm pregnancy termination.
  • Spay during pregnancy: Spaying a pregnant female involves more risk because the pregnant uterus is larger and more engorged.
  • Allow the female to deliver the puppies: This can result in homeless puppies and contribute to pet overpopulation.

Preventing an unwanted pregnancy is best accomplished by spaying your female.

Abb. GG99IDDF: Canine Tie.
This is a photograph of the tie which results when a male dog breeds a female dog. At this time, the male has already ejaculated and pregnancy cannot be prevented.

Update version: 4/24/2014, © Copyright by
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