How long is a large dog pregnant before giving birth?

A dog’s pregnancy lasts about two months. One month after mating, take the dog to a vet for an ultrasound to confirm pregnancy.

The first 30 days have an unstable fetal heartbeat, so avoid strenuous exercise to prevent threatened miscarriage. Keep the mother calm.

Around day 45, an X-ray can show how many puppies there are and how they are developing. Bones are visible by then.

The X-ray also helps estimate the due date, so you can prepare for whelping in time.