The use of progesterone tests in dog breeding to pinpoint ovulation is becoming more widely used.  There are several tests available but the most reliable test is a blood test with blood drawn by a veterinarian and sent to a lab for processing.  Results can usually be obtained with 24 to 72 hours.  The rationale for using progesterone tests is that increased numbers begin in close proximity to preovulatory surge in gonadotrophins and continue through ovulation and estrus.  When progesterone levels reach certain levels they can signal the stage of estrus the female is.  Prediction of birth date of the pending litter can be very accurate if ovulation date is known.  Puppies deliver with a day or two of 9 weeks gestation in most cases.  It is not possible to determine pregnancy using progesterone tests once a breeding has taken place, however.  This is due to the fact that, in dogs, progesterone levels remain elevated throughout the estrus period.