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Hormone Levels: Determining Breeding Times and Whelping Dates (REVERSE PROGESTERONE).

Understanding how the hormone levels change can help in determining the best time to breed and when to anticipate whelping.
Progesterone levels and luteinizing hormone (LH) levels are the best indicators of when ovulation will take place and when is the best time to breed. Also is useful in determining whelping dates, allowing the owner prepare for the c-section (cesarean) weeks in advance.

Progesterone levels and breeding.

The progesterone test can be done every 2-3 days starting about  3-5 days into the heat. The beginning progesterone levels are typically less than 1.0 ng/ml  until the day before the LH surge. 
The day of the LH spike, serum progesterone concentrations are 2-3 ng/ml; the day following the LH surge, the serum progesterone concentration is 3-4 ng/ml.
Ovulation occurs at a progesterone level of 5 ng/ml.

Timing of breeding

The goal is to identify when the progesterone level  reaches 3.5 ng/ml so the mating schedule  can be set up, or the  Veterinarian and owner of the male dog can be notified, they should be prepared to collect and ship the semen sample.
Optimal time depending of semen and types of breedings are:
Natural breeding should occur 3 days after the 2.5 ng/ml mark. Sperm in fresh semen survive 5-7 days after insemination.
Artificial insemination  using fresh chilled semen  should be used for a 1-time breeding.   Insemination should take place  4  days  after the  progesterone reaches the 2.5 ng/ml mark or 48 hours after the 5 ng/ml mark. Sperm in chilled semen survive 48-72 hours after insemination.
With Transcervical Insemination, the semen should be deposited into the cervix to increase the pregnancy accuracy. 
Artificial insemination using frozen semen should be performed 5 days following the 2.5 ng/ml mark or 72 hours after the 5 ng/ml mark.
Sperm in frozen semen survives less than 24 hours after insemination.  
Frozen semen is ideally deposited directly into the uterus through surgery to increase the chance of pregnancy.
Progesterone levels during pregnancy and whelping ( REVERSE PROGESTERONE ).
After ovulation, progesterone concentrations continue to increase for 2-3 weeks, finally reaching 10-80 ng/ml. This level is necessary to maintain a pregnancy.

The progesterone level will remain at this level for about 60 days whether or not the dog is bred, and whether or not she is pregnant.
About 48 hours before whelping, the progesterone level drops to the 2 ng/ml range and within about 24 hours of whelping, the level drops to
the 1 ng/ml range.This can help determine the proper timing of a c-section.
By correctly determining the whelping time, it can prevent puppies from being taken by c-section too early and thereby decreasing their chance of survival.
The following chart indicates the estrus cycle (by days), the hormone levels, breeding times, and whelping dates.

It is important for you to understand that while the "average" bitch may ovulate on day 12 to 14, not all bitches do so. A bitch may be different on each cycle. Counting days may mean nothing, as she could ovulate as early as day 4, or later than day 20. Is highly  recommended  to  do  the  progesterone blood  test  (available in home)  to  determine  the precise time that ovulation is occurring, increasing the litter size and  determing the correct day  for    C-section for delivery puppies.
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