How long is a dog’s pregnancy
The duration of pregnancy is much more predictable when the date of ovulation is known. In this case, labor will begin on the 62nd-64th day from the day of ovulation.
A peculiarity of dogs is the discrepancy between the time of ovulation and the fertile period: this means that after ovulation, the egg needs about 48 hours to mature and be able to fertilize, and 48-72 hours after maturation, the egg dies. Sperm, in turn, can survive in the reproductive tract for up to 7 days. Accordingly, if mating is carried out a few days before ovulation, fertilization will occur much later, and the pregnancy will seem longer. If mating is carried out, for example, 3-4 days after ovulation, sperm will fertilize those eggs that have not yet undergone degeneration, and the pregnancy will seem shorter.
The timing of mating may be based on clinical signs, the bitch’s attractiveness to males and her acceptance of mating, changes in vaginal discharge (from heavy hemorrhagic to lighter), and counting the days from the onset of estrus. Not all dogs have a fertile period between days 11 and 13 of estrus, and for a large percentage it may vary from cycle to cycle.
The vaginal smear test detects the presence of superficial vaginal epithelial cells that appear in direct proportion to the increase in estrogen hormone levels. The results of a vaginal smear test can detect signs of estrus, the stage during which ovulation occurs, but it is impossible to determine the time when it occurs. This is an important method, but not very accurate.
The most accurate method for determining the time of ovulation in dogs is testing the level of the hormone progesterone in the blood. Progesterone begins to rise even before ovulation, which allows you to start taking measurements in advance. The level of progesterone at the time of ovulation is approximately the same in most dogs. As a rule, several measurements are required (once every 1-4 days).
In practice, starting from the 4th-5th day of estrus, a cytological examination of vaginal smears should begin, then (from the moment the estrus picture is detected in the smear) blood tests for the hormone progesterone and an ultrasound examination of the ovaries are carried out.
The length of a dog’s pregnancy varies considerably and can be anywhere from 57 to 72 days from the day of mating. In essence, the length of pregnancy directly depends on the methods used to determine the time of the fertile period (the period when a dog can become pregnant).