Pregnancy Testing in Dogs

Is there a blood test to detect pregnancy in dogs?

Yes. There is a blood test that detects pregnancy by measuring the level of a hormone called relaxin. The developing placenta produces the hormone after an embryo implants in the uterus. Relaxin can be detected in the blood in most pregnant dogs as soon as 22 to 27 days after breeding. Levels remain high throughout pregnancy and decline after the pregnancy ends.

Can the relaxin test tell the difference between pregnancy and pseudopregnancy?

Yes. Dogs with pseudopregnancy do not produce relaxin, so the test can help distinguish pregnancy from pseudopregnancy. Pseudopregnancy, also called false pregnancy, causes a female dog to look and behave as if she is pregnant when she is not. Signs develop after a heat cycle. There is no placental development during pseudopregnancy, so relaxin is not produced, and pregnancy tests will be negative.

Does a single negative relaxin test mean a dog is not pregnant?

Not necessarily. A negative result may indicate that a dog is not pregnant. However, a false negative result means the test is negative even though the dog is pregnant. This can happen if the test is performed too early, before the placenta has started to produce relaxin. 

A dog with a negative result on an initial test performed 22 to 27 days after breeding should be tested again one week later. Repeat testing is especially important in early pregnancy and when the breeding dates are unknown. In most cases, two consecutive negative tests, one week apart, confirm that a dog is not pregnant. Rarely, a third test may be needed 31 to 34 days after breeding.

Small and toy breeds may not produce enough relaxin to generate a positive test, especially if they are carrying only one or two puppies. In these dogs, your veterinarian may use another method to check for pregnancy (see below). 

Does a positive relaxin test mean a dog is pregnant?

A positive relaxin test indicates that a dog is pregnant at the time of the test. Conception has occurred, the embryo has implanted, and a placenta is developing. However, it does not confirm that the developing puppies are alive.

Does a positive relaxin test mean that live puppies will be born?

Not necessarily. The test cannot predict whether the pregnancy will end with the birth of live puppies. Unfortunately, there are many reasons why pregnancies fail, and puppies can be lost at any stage of pregnancy, including at birth (whelping). Sometimes a dog will test positive for relaxin on the first test but negative on a later test. This may indicate pregnancy loss, even though the dog may not have shown any sign of a problem.

Are there other ways of detecting pregnancy in dogs?

Other methods include abdominal palpation, X-rays, and ultrasound.

Abdominal palpation

The traditional method of detecting pregnancy is careful abdominal palpation. Your veterinarian gently presses on your dog’s abdomen to feel for swellings in the uterus caused by developing puppies. The accuracy of this method depends on several factors:

• The dog’s temperament, size, and body condition
• The timing of the examination, with the optimal time between 3½ and 5 weeks of pregnancy
• The number of developing puppies
• The experience of the person performing the examination

Palpation cannot reliably determine whether the puppies are alive.

Abdominal X-rays

Abdominal radiographs (X-rays) can detect pregnancy during the final third of pregnancy, roughly 43 to 45 days after breeding, or about three weeks before whelping, when the puppies’ bones become visible. 

Radiographs are the best way to determine the numbers of puppies in a litter. The viability of the puppies can usually be determined, although there are situations when this could be difficult. For example, the sudden death of a full-term puppy in the uterus would be difficult to detect on an X-ray. 

Abdominal ultrasound

The most reliable way to detect and monitor pregnancy is abdominal ultrasound. Developing embryos can be detected as early as three weeks after breeding. Ultrasound can also help your veterinarian assess whether the developing puppies are alive and monitor their development during pregnancy.