Misalliance in dogs: what to do after an unwanted mating 

How likely is an unwanted pregnancy in dogs?  

Female dogs usually come into season around every 6 months, although this does vary between breeds and between individuals. They are fertile for around 2-3 weeks. Females will only allow a male dog to mate with them when they are in their fertile window. Unfortunately this means that the chances of pregnancy, even from a single mating, are pretty high! 

When can you test for pregnancy? 

Pregnancy in dogs lasts around 63 days. The earliest you can reliably test for pregnancy is around 22 days after mating. The options for pregnancy testing in dogs include: 

Blood test 

Your vet can take a blood test for the hormone relaxin. Relaxin is released by the placenta as it develops. It’s pretty reliable and can be taken from 22 days after mating. However, if the result is negative it is advised to repeat the test around 10 days later. This is because false negatives are possible early on, and especially in small litters. 

Ultrasound 

Ultrasound can be used from 21-30 days after mating and can tell you if the puppies are alive, so this is often the preferred method of pregnancy detection in dogs. It can be very tricky to tell how many puppies there are with an ultrasound, especially in larger litters. An x-ray is more reliable for this purpose, from 47 days onwards.  

Palpation 

This involves the vet palpating your dog’s tummy, to feel for puppies. While simple and inexpensive, it can’t be done until around 28 – 35 days after mating, and is not very accurate. It is easy to miss a puppy (especially early on in pregnancy, or if there is only one puppy) and equally as easy to mistake a build up of faeces (poo) for a puppy! 

What to do if your dog accidentally mated 

Since pregnancy in dogs only lasts around 63 days, don’t delay in contacting your vet! Especially if the pregnancy was accidental and unwanted. If you have an entire female dog and she does get caught unexpectedly, these are your options: 

Keep the puppies 

One option is to take the risk, and wait and see if your dog is pregnant. This is only advisable if you are prepared to keep the puppies if she does turn out to be in pup. 

You need to think very hard about this one! While it may sound exciting, and certainly can be rewarding, rearing puppies is a huge responsibility. It takes a lot of hard work, time and great expense. You also need to be sure that you can find suitable homes for all of the puppies. With so many puppies and dogs in rescues waiting for homes, this is getting harder and harder. Not knowing who the father is won’t help, as he may have health conditions that could pass to the puppies. This may deter future owners, especially responsible ones (which naturally you would want for the pups!). 

You also need to consider the health of, and potential risks to, your dog; and whether it would be safe for her to carry a litter. In addition, the health of any possible puppies needs to be considered! For example, does your dog have any medical conditions that they may pass to their puppies, such as elbow dysplasia or allergies (atopy)? Your vet can chat through the risk with you for your dog as an individual. 

Neuter 

If you don’t wish to go through with the pregnancy and have no plans to breed from her in the future, you can spay (neuter) your dog. This will end the pregnancy and prevent any future litters.  

Neutering during pregnancy is slightly more risky than a routine spay, as the blood supply to the area is much larger. The earlier in pregnancy you neuter, the better. A pregnant spay is still a surgery that vets will be experienced in performing. It’s a case of weighing the risk/benefit. 

If you want to be sure, you could consider a blood test or ultrasound first, to see if she is definitely pregnant. Of course this means waiting until 22-28 days post mating. 

Medical management 

Progesterone is a hormone needed during pregnancy for implantation to occur, and for the placenta to develop. There is a medication available with the active ingredient aglepristone, which blocks progesterone receptors, so blocks the action of progesterone. 

Aglepristone is given as two injections, 24 hours apart. It can be given from 10 to 45 days after mating. However, the sooner the better! When given early in the pregnancy it is not only more effective, but also less unpleasant for your dog. If the injections are given 10-25 days after mating, the pregnancy is usually resorbed. From around 25 days onwards, the injections cause abortion and your dog would have to pass the foetus(es).  

Possible side effects of aglepristone include: 

• Discomfort, itch and inflammation at the injection site 

• Reduced appetite 

• Lethargy 

• Vomiting and diarrhoea 

• Vulval discharge  

• Hypersensitivity reactions (which are rare) 

You can ask your vet to talk you through the full list of possible side effects. 

Although it is highly effective (working in around 90% of cases when used in early pregnancy), it’s safest to have an ultrasound scan 10 days later, to check if the treatment has worked (if it’s at least 21 + days post mating).  

It’s important to make sure no further matings occur, as it does not prevent future pregnancies. 

Pregnancy prevention 

As with most things, prevention is better than cure! 

There is no ‘contraceptive pill’ for dogs. So, what are the birth control options for female dogs in the UK?  

Neutering 

This is the most reliable method of contraception for dogs of either sex. It is permanent and non-reversible. Spaying is the surgical removal of a female dog’s ovaries +/- uterus (womb). This can be performed via keyhole surgery in some clinics.  

Hormonal implants 

There are hormonal implants available that are sometimes used to simulate the effects of neutering. However, these are not licensed for use in female dogs, and tend to be expensive, especially as they need replacing every 6-12 months. 

Physical prevention 

This involves keeping your dog away from intact (not neutered) male dogs when they are in season (for the full 3-4 weeks). It’s not bullet proof, and with the best will in the world, accidents do happen! 

It’s important to keep your dog on a lead during walks too, and to walk in quiet areas. After all, even if you keep her on a lead, this does not prevent a frisky, off-lead, entire male from running up to them! Some people find using private, secure dog walking fields less stressful during this time. While this is an added cost, it does prevent accidental matings on a walk. 

Take home message 

If you think your dog has accidentally mated, and she is entire and so could become pregnant, contact your vet for advice as soon as possible!  

There are options available, which your vet can talk through with you. They can advise you on the risk/benefit of each option for her.  

Timing is important for each option, so the sooner you ask your vet for advice, the sooner a plan can be put in place. 

Further reading 

Canine Estrous Cycle – Cornell 

I want to breed my dog- what checks should I get done on the father? 

Dog Breeding – Pet Health Library