Why the range is so wide
A dog's gestation is actually very consistent when measured from the right starting point. Vets count it as 65 days (give or take a day) from the LH hormone surge, 63 days from ovulation, or 57 days from the first day of diestrus seen on a vaginal smear. The variation comes from mating. A female may accept a male several days before she ovulates, and sperm can survive inside her for up to a week. So the calendar date of mating can be several days away from conception.
Does breed or litter size matter?
Only slightly. Very small litters (one or two puppies) sometimes run a little longer, and large litters a little shorter. Breed has little effect on the length, but brachycephalic breeds like Bulldogs and French Bulldogs often need a planned C-section.
Pinning down the due date
- Progesterone tests during heat find the ovulation day, and give the most accurate due date (±1 to 2 days).
- Ultrasound from about day 25 confirms pregnancy, and fetal measurements can estimate age.
- X-ray after day 45 counts the puppies and helps judge timing.
Get your dates with the dog pregnancy calculator.
Frequently asked questions
How many weeks is a dog pregnant?
About 9 weeks. Counted from mating, it can range from just over 8 weeks to almost 10.
Can a dog be pregnant for 70 days?
Rarely, if counted from an early mating. But call your vet if she reaches day 68 from mating (or 65 from a confirmed ovulation) without signs of labor.