The Cat Gestation Period - How Long Are Cats Pregnant For?
The cat gestation period is generally defined in most textbooks as: the number of days between a "successful mating" and the birth or parturition of the fully developed kittens. A successful mating, also called a "fertile mating," is a mating (copulation) between male and female cats that results in the ovulation of eggs (ova) from the female cat's ovaries and their fertilization with male spermatozoa (sperm) within the oviducts of the uterine tract. Depending on which textbook you read, the cat gestation period is generally stated as being somewhere between 61 and 69 days long (NOTE - I have seen feline gestation period figures as short as 56 days right through to as long as 72 days), with an average of 63 to 66 days.
The reason for the huge variation in the figures stated for the length of the cat gestation period is the nature of the feline reproductive cycle itself. Female cats are "induced ovulators," which means that they require the mating stimulus of a male cat (the friction associated with copulation) if they are to ovulate their ova (eggs) into their uterine tract for fertilisation (i.e. a "successful mating" or "fertile mating" as per the definition used in the paragraph above). Generally, several matings are required (8-12 copulations or more), often over a period of days, before the female cat becomes stimulated enough to ovulate her eggs. It is uncommon for a single
mating between male and female cats to result in successful ovulation (less than half of female cats ovulate after a single copulation). Once enough mating stimulus has been provided, it generally takes the female cat a further 24-52 hours after the successful mating to release the eggs into the uterus tract.
It is because the cat gestation period is defined using a starting point of: "a successful mating" that the wide variation in stated feline gestation periods exists. Female cats often require several matings over several days in order to ovulate and become pregnant and the cat breeder or pet owner, unsure as to which of these witnessed matings is the so-called "successful one," often can not tell where to start the count from. Does s/he start the gestation period count from the first mating seen, which could have been many days ago, or from the most recent one? Hence the variation in the length quoted for cat pregnancy length: people who start the count from the first witnessed mating will often find longer feline gestation periods and people who start the countdown from the most recent copulation witnessed may well have shorter feline gestation period figures.
If breeding conditions are more tightly controlled and the in-heat female cat is only allowed 1 or 2 days of copulation, then feline gestation periods will usually fall within a more refined timespan of about 63 to 68 days (i.e. more accurate). This kind of breeding control can be achieved when cat breeders deliberately limit the time that the in-heat queen can be in contact with an entire tom to a couple of days. The chances of a successful pregnancy may be reduced if such limitations are applied (a particular queen might not ovulate in only two days of mating), but the gestation start date is much more accurately known.
Pin-pointing the feline gestation start-point (and hence the kitten due-dates) is much harder in female cats that have long "heat periods" (some female cats will show signs of being "in-heat" and will even stand to have a male cat mate with them for a period of up to 21 days). Some of these "longer-heat" female cats may undergo repeated matings early on in their season and yet not ovulate (even though they are large enough in size to secrete enough estrogen to cause the cat to show signs of heat and to 'stand for mating,' the ovarian follicles are presumed to be "not ripe enough" yet to ovulate), but days later they will mate again and have a successful ovulation (because the follicle/s are now ripe). In such cases, unless progesterone levels are used to pin-point the time of ovulation (see next paragraph), the particular mating that induced the ovulation to occur is unknown and, thus, so is the start-date of the cat pregnancy also unknown.
Because ovulation in the female cat is accompanied by a rapid surge in blood progesterone levels (the ripe ovarian follicle that ovulated transforms into a progesterone-secreting nodule called a corpus luteum
immediately after ovulation), some breeders and vets elect to measure blood progesterone levels daily or every second day during the feline mating period to increase their accuracy at determining the cat gestation start-date. An increase in blood progesterone levels over 2.5ng/ml is generally suggestive of ovulation having occurred and so the first day that progesterone levels top 2.5ng/ml is usually stated as being the first day of pregnancy (the first day of the cat gestation period). When progesterone levels are used to gauge ovulation, the feline gestation period usually falls within a more refined timespan of about 63 to 66 days (i.e. more accurate) from the time of the first progesterone level increase.
For those of you who do not wish to measure serial progesterone levels, the female cat herself may give you a rough behavioral indication of when ovulation has occurred. Once a cat ovulates, she tends to go off heat (stop showing heat symptoms - see our feline estrus page for information on cat heat signs
) within 24-48 hours. If the change in behavior is very obvious, then a cat owner or breeder might be able to make an approximate guess that ovulation occurred 1-2 days ago and use that date (the 2-days-ago date) as the estimated start point for the cat gestation period. It is not as accurate as progesterone mapping, but it might be useful for those of you who just want a rough approximation.
For more on the estrus behaviour of the female cat and how the symptoms of heat are hormonally induced (how it all works), please see our informative "female cat in heat" page.
In summary - How long are cats pregnant for?
Between 61 and 69 days, with an average of 63 to 66 days. Greater accuracy in the determination of cat pregnancy length can be achieved by limiting male and female cat copulation periods to about 1-2 days or by measuring serial blood progesterone levels daily or every other day (every second day) during the feline estrus and mating period.
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Cat Gestation Period - References and Suggested Readings:
1) Verstegen J, Feline Reproduction. In Ettinger SJ, Feldman EC, editors: Textbook of Veterinary
Internal Medicine, Sydney, 2000, WB Saunders Company.
2) Feline Reproduction. In Feldman EC and Nelson RW: Canine and Feline Endocrinology and Reproduction, 2nd ed. Sydney, 1996, WB Saunders Company.
3) The Pelvis and Reproductive Organs of the Carnivores. In Dyce KM, Sack WO, Wensing CJG editors: Textbook of Veterinary
Anatomy, 2nd ed. Sydney, 1996, WB Saunders Company.
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