So, let’ s look at the mechanisms that regulate the physiologic birth: first, the birth duration of a female dog is nine weeks, so sixty-three days, from the day in which it has the ovulation, this is an important concept because in many cases the birth duration computations are made from the day in which coupling happens. 

A coupling can happen several days before the ovulation, but also several days after it, meaning that the birth duration, if calculated from the coupling, lasts from fifty-eight to sixty-seven days. 

As a confirmation of that, to know when a female dog ovulated, it’s possible to do some computations, knowing the date in which she coupled, what the heat day was, and the birth date.

Let’s do an example of a female dog that coupled on the 12th heat day and gave birth sixty-seven days after, the computation will be 67-63 (birth duration from the ovulation day) = 4 days of waste that will be detracted from the 12th heat day, the computation will always be 63-58 = 5 days of waste that will be added to the heat day in which the coupling happened so 12+5 = 17, ovulation happened in the 17th heat day.

A difference in the birth duration so wide, if calculated from the coupling, is justified from the spermatozoa survival for many days inside female genital tracts, documented also seven days after the coupling, and the possibility, from the ova too, to be fertilized until about four days after the ovulation, it’s obviously more we go away from the moment of maximum fertility and less will be the fertility, from that it derives the risk of a no-birth or a small litter than the breed average.

Something important to remember is that a characteristic of the canine species is the fertilization of the ova from the spermatozoa happens forty-eight hours later than the ovulation, so it will be necessary to wait two days after the ovulation to obtain the maximum fertility!

Knowing the day in which the female dog ovulates will be necessary also to know the presumed birth day, if there will be a delay over the twenty-four hours than the specific date it will be important to ascertain the fetuses state of health and to evaluate if the physical parameters are good to wait or to schedule a “caesarean” delivery or a pharmacological induction to pet birth.