Quantitative progesterone is measured in a serum sample taken 18 - 25 days post service. This test is very useful for thoroughbred mares, where timing is critical, but further testing at a later date is required to confirm pregnancy (see below). | Quantitative progesterone is measured in a serum sample taken 18 - 25 days post service. This test is very useful for thoroughbred mares, where timing is critical, but further testing at a later date is required to confirm pregnancy (see below). |