Until recently, there has been no blood or urine test that would reliably predict pregnancy in dogs. A commercial relaxin assay (ReproCHECK, Synbiotics Corp.) has recently become available as a canine pregnancy test. Relaxin hormone is produced by the ovary and placenta of pregnant bitches and becomes elevated by about mid-gestation. In contrast, relaxin concentrations are reported to be undetectable in nonpregnant and pseudopregnant dogs.

The usefulness of this assay for detecting pregnancy in dogs has been under evaluation at Antech Diagnostics. To date, we have data on 33 bitches that were bred and followed to term. Relaxin concentrations were measured at least 30 days post-breeding. Fifteen dogs had positive relaxin tests and all of them whelped live puppies. There were no false positive results. Eighteen dogs had negative relaxin tests, and 14 of these dogs had no puppies. Of the other 4 dogs, 2 each had 1 viable puppy, 1 dog had 1 stillborn puppy, and 1 had 3 puppies with 1 born dead. These were false negative relaxin test results and occurred with small litter size. An additional 2 dogs carrying small litters (1-2 pups) had positive relaxin tests just before whelping.

Conclusion: An elevated relaxin concentration is a reliable test for pregnancy in dogs. False positive results rarely occur. False negative results may occur when pregnant bitches carry small litters, and/or one or more of the puppies are nonviable.

Specimen Requirements     0.5 mL separated GTT or BTT plasma
Turnaround Time      2–4 days