Species: Canine and feline

Specimen:  Serum or plasma

Container: Red top tube (serum), EDTA, sodium citrate or lithium heparin (plasma)

Special handling/shipping requirements: 

Relaxin will start to degrade after about 4 hours, so samples kept at room temperature should be analysed as soon as possible. The sample can be kept in the fridge for up to 48 hours and should ideally be kept chilled during transport to the lab. Separated serum or plasma samples may be kept frozen for later analysis.

Collection protocol: 

Sample at 31 days after the last mating. If the mating date is unknown, and the test gives a negative or suspicious result then repeat in 7-10 days to confirm. 

General information about the disease: N/A

General information about when this test is indicated:

Pregnancy in the bitch/queen can be confirmed by measuring concentrations of the hormone relaxin. Relaxin is detectable from about 20 days post mating. By day 28 the test is positive 80% of pregnant canines/felines. However, depending on factors such as breed or size of bitch, litter size and time of mating relative to the LH surge it may not become positive to 31 days then remains positive for the remainder of the gestation. Pseudopregnancy does not give a positive result, as there is no placenta. As with all pregnancy tests, a positive result reflects the status at the time of testing and does not guarantee that the animal will remain pregnant. Relaxin levels decrease within 2-3 days of the loss of a viable pregnancy.

Comparison with other related tests: 

Relaxin is superior to progesterone measurement for pregnancy detection in both species. Progesterone cannot reliable distinguish between pregnancy and pseudopregnancy in dogs or cats, and similar levels of progesterone are produced in pregnancy and dioestrus in dogs. Relaxin does not increase during pseudopregnancy in dogs or cats or in non-pregnant bitches in dioestrus.