Meddor
How long a pregnancy lasts
According to the Merck Veterinary Manual, pregnancy lasts 62 to 64 days in dogs and about 65 days in cats. But counting from the mating date gives a wide window:
| Counted from | Birth |
|---|---|
| Dog: first mating | 58 to 72 days later |
| Dog: LH surge or progesterone rise | 64 to 66 days later |
| Dog: 1st day of diestrus | 56 to 58 days later |
| Cat: mating | 64 to 66 days later, for a pregnancy of 60 to 65 days |
Why such a gap in dogs? Sperm can survive nine days or more in her reproductive tract, and ovulation doesn’t necessarily fall on the mating day. Hormone tests and smears done by your vet give a far more precise date. Breed, number of previous pregnancies and litter size also play a part.
Cats ovulate because they’re mated. Merck advises several matings over 2 to 3 days: count from the first one, and the date remains an estimate.
Check-ups along the way
- Around 21 days: your vet may be able to feel the embryos, if the animal cooperates.
- 25 to 35 days: the best time for an ultrasound, which also checks the foetuses are alive. Before 21 days, it can miss them.
- After 22 to 27 days, in dogs: a blood test (relaxin) can confirm the pregnancy.
- Around 42 to 45 days: skeletons become visible on X-ray.
- After 55 days: an X-ray is the best way to count the litter.
These days are counted from conception: from a mating date, they’re approximations.
As the birth approaches
In most dogs, rectal temperature drops 8 to 24 hours before giving birth, to between 36.7 and 37.8 °C (98.1 to 100 °F). The vulva relaxes and the teats swell, but these signs aren’t reliable for predicting the day.
A pregnant cat needs more food: according to the Merck Manual, about 25% more during the last 3 weeks. Your vet will tell you which food to give her.
Frequently asked questions
My dog was mated twice: which date should I use?
The first one. Merck counts the 58 to 72-day window from the first mating she accepted.
The due date has passed and nothing is happening
Call your vet. Don’t try to bring on the birth yourself: according to Merck, there’s no safe, predictable way to induce it.
How do I know she’s really pregnant?
With an ultrasound, the most useful exam, between 25 and 35 days. A rounder belly isn’t proof.
Sources
- Merck Veterinary Manual, “Approximate Gestation Periods”.
- Merck Veterinary Manual, “Whelping and Queening in Bitches and Queens”, June 2025: due dates, temperature drop.
- Merck Veterinary Manual, “Pregnancy Determination in Bitches and Queens”, January 2026: palpation, relaxin, ultrasound, X-ray.
- Merck Veterinary Manual, “Breeding Management of Bitches”, July 2025: sperm survival.
- Merck Veterinary Manual, “Management of Reproduction of Cats”, August 2025: mating in cats, pregnancy length, feeding.