For each species, the length of gestation varies. If you plan to breed your bitch, it is essential to get information to best prepare the arrival of the puppies. Likewise, it can be vital to know the theoretical term of gestation because an overrun may require surgery. Here is some information to know before breeding.

Fertilization

To calculate the date of the presumed term, it is first necessary to choose the starting point. Indeed, in theory, gestation begins at the time of fertilization and then lasts 61 days (to one day). However, the exact time of fertilization is generally not known. The calculation of the term must therefore be based on an easily identifiable event. Two options are possible.

L’ovulation

The most precise is to determine the moment of ovulation. This generally requires repeated hormonal dosages during heat. Once the day of ovulation has been identified, the gestation period is 63 days (to within one day). This technique is preferable because it is much more reliable. However, it requires hormonal monitoring, at the veterinarian, during periods of heat.

Mating

The other exploitable starting point is mating. Following mating, the sperm will survive for a few days, waiting for ovulation. This period is variable and depends on the stage of the bitch’s cycle at which the mating takes place. The gestation period calculated on the basis of the service date is therefore less precise. It varies from 57 to 72 days.

In some cases, the date of service is unknown. Sometimes the heat has even gone unnoticed and gestation is a fortuitous discovery. There are, however, techniques for estimating the date of the term, although these are less precise. This requires medical imaging exams.

The earliest is the abdominal ultrasound. Fetuses can be visualized from the 3rd week of gestation, or even from the 15th day. If they are observed, they can be measured. With these measurements, the number of weeks of gestation remaining can be estimated.

Another technique is radiography. This concerns rather the advanced stages. Indeed, on the x-ray, the skeletons of the puppies are visible from the 45th day after fertilization. However, the visibility of the bones depends on their state of mineralization, which is a process which progresses little by little until the birth. Thus, some bones will be mineralized and therefore visible earlier than others. For example, the skull can be seen 20 to 22 days before term when the pelvis does not become visible until 6 to 9 days before. The last elements to mineralize are the teeth: if these are visible on x-rays, childbirth should take place within 3 to 5 days.

At the end of gestation, the bitch will exhibit a different behavior: she will tend to make her nest and seek contact or, on the contrary, isolate herself more. This announces the birth in the days to come. However, it can be complicated to determine if the gestation is ending or if the term has already passed. Indeed, if the date is estimated on the time of the mating, the period between the 57th and 72nd day is quite large. In this case, several clues can be used to locate the birth.

The most precise technique relies, again, on hormonal assays. Repeated monitoring of the blood progesterone level can detect the day of parturition with 80% certainty. Indeed, after going under a certain threshold, most bitches give birth within 48 hours.

Another technique, easier to implement, is to monitor the bitch’s rectal temperature. It can be taken very easily using a baby thermometer, by pushing the tip 1 to 2 cm and pressing the end against the lining of the rectum. In most cases, rectal temperature drops before parturition. Thus, it is advisable to take the temperature every day, several times a day, and to calculate the average of the values. If a measurement indicates a value lower than the average by more than 1 ° C, the farrowing should take place within 8 to 14 hours. However, this temperature drop is not systematic in all bitches.

In conclusion, a bitch’s normal gestation period normally lasts 61 days but, based on observable events, this duration is estimated at 63 days after ovulation and 57 to 72 days after mating. Precisely estimate the term is necessary because a cesarean section will have to be performed if it is exceeded, so as not to endanger the bitch and the puppies. It is therefore strongly recommended to make an appointment with your veterinarian even before breeding to determine together the moment of ovulation and organize the monitoring of gestation. He will be able to advise you on vaccinations, antiparasitic treatments and hygienic measures (food, organization, etc.) necessary for the good health of the bitch and the puppies. If the gestation was not planned, it is still possible to estimate the date of the due date to organize the best.