How long does a dog’s pregnancy last?

The duration of pregnancy is much more predictable when the date of ovulation is known. In this case, labor will begin on the 62-64th day from the day of ovulation.

A feature of dogs is the discrepancy between the time of ovulation and the fertile period: this means that after ovulation, the egg takes about 48 hours to mature and be able to fertilize, and 48–72 hours after maturation, the eggs die. Spermatozoa, in turn, are able to 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, spermatozoa will fertilize those eggs that have not yet undergone degeneration, and the pregnancy will seem shorter.

Timing of mating may be based on clinical signs, the bitch’s attractiveness to males and her acceptance of mating, changes in vaginal discharge patterns (from intense hemorrhagic to lighter), and counting days from the onset of estrus. Not all dogs are fertile between days 11-13 of estrus, and for a large percentage it can vary from cycle to cycle.

The method of determining the fertile period using the study of vaginal smears allows you to detect the presence of surface cells of the vaginal epithelium, which appear in direct proportion to the increase in the level of estrogen hormones. According to the results of a cytological examination of vaginal smears, signs of estrus can be determined – the very stage during which ovulation occurs, but it is impossible to determine the time when it occurs. This is an important method, but not accurate enough.

The study of the level of the hormone progesterone in the blood is the most accurate method for determining the time of ovulation in dogs. 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 in most dogs is about the same. As a rule, several measurements are required (1 time in 1-4 days).

Ultrasound examination of the ovaries is another method that significantly improves the accuracy of determining the time of ovulation.

In practice, from the 4–5th day of estrus, a cytological examination of vaginal smears should be started, then (from the moment an oestrus pattern is detected in the smear), blood tests for the hormone progesterone and ultrasound of the ovaries are carried out.

January 30 2018

Updated: July 18, 2021