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. Relaxin levels decrease within 2-3 days of the loss of a viable pregnancy. Refer to relaxin test for specific test protocols.