Canine Relaxin

Pregnancy in the bitch can be confirmed by measuring concentrations of the hormone relaxin. Relaxin is produced by the placenta from about 21 days post mating. By day 28 the test is positive 80% of pregnant bitches. However, depending on factors such as breed, size of bitch, litter size and time of mating relative to the LH surge it may not become positive to 33 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.




1 ml whole blood       


Lithium heparin (green top) tube, NaCitrate may also be used.

EDTA anticoagulated blood and serum are not suitable.

Collection protocol:

Sample at 33 days after the last mating. If the mating date is unknown, and the test gives a negative or equivocal result then repeat in 7-10 days to confirm.

Special handling/shipping requirements:

The sample can be kept in the fridge for up to 48 hours. Plasma samples may be kept frozen for later analysis.