Submitted by CCLRC member Autumn Davidson, DVM


An unplanned breeding between sexually intact dogs during a time when the bitch could be fertile (in estrus). Sometimes it is hard to tell if the breeding actually occurred (dogs were found together, unsupervised) or if possible (sexually immature dog). It is also difficult to tell in some cases whether the bitch was at a likely fertile time of her cycle.  


  1. Spay: if the bitch is not intended for breeding, plan to have her spayed as soon as she is out of estrus. This is the easiest and least cost option of pregnancy prevention.
  1. Early treatment: if the timing seemed appropriate and fertility is likely, we can terminate the litter in the first 2-3 weeks. This involves injections of a compound twice per day for four consecutive days. The time when this treatment starts is crucial for success and an exam within one week of the mismating is needed to schedule these treatments. In some cases a second exam is needed to accurately determine when to do this treatment. The advantage of this treatment: relatively easy, lower cost than mid-term abortion. The possible negatives: not guaranteed to work (about 80% effective), owners must bring in female for the injections twice per day and each treatment takes about one hour. Then they must return for follow up ultrasound 30 days after the breeding. In addition: the medication used for this procedure is Lutalyse: a natural prostaglandin. Each injection can cause nausea and irritability for approximately 30 minutes.
  1. Mid-term abortion: 30 days after the breeding, we will do an ultrasound exam to determine if there is a pregnancy. At that time medications can be given to cause the uterine contents to abort. This takes 4-10 days of treatment. The advantage: we are only treating when we know there is a pregnancy and we treat to effect-until all fetuses are expelled. The negative: nausea and irritability with each treatment–although tolerance to the medication usually develops over the treatment period.

Note: There is no negative impact on fertility with option #2 or #3. We can see a return to estrus sooner than expected. She can be bred at that next cycle, or it can be skipped.