Did you know the gestation time for cats and dogs is 2 months ! At 28 days the foeti are detectable on ultrasound and by 53 days the foeti have calcified, making them radioopaque, and visible on Xray. Generally ultrasound is used to confirm pregnancy as counting is not as accurate with this method. Xrays are often used to determine the number of puppies so the breeder knows how many to expect during a natural birth. This can help to determine if there are any puppies or kittens in distress and when surgical intervention may be needed.
Neither ultrasound nor Xray cause any harm to the mother or the growing foeti.

Can you count the number of puppies and kittens in the following photos ? Scroll down for the answers. 

Answer to how many puppies and kittens: photo 1:6 puppies, photo 2:5 puppies, photo 3:4 puppies, and photo 4:5 kittens.