A full-term pregnancy for a dog usually lasts 63 days. At 42 days of pregnancy, the skeletons of the fetuses start to calcify and can just be seen on a radiograph (“x-ray”). By 50-55 days of pregnancy, they are sufficiently visible to be able to count skulls and spines to try to determine litter number. How many puppies is this mom expecting?
![](https://www.centennialah.ca/wp-content/uploads/sites/304/2022/06/chihuahua-x-pregnant-abd-rad.jpeg)
![](https://www.centennialah.ca/wp-content/uploads/sites/304/2022/06/chihuahua-x-pregnant-abd-rad-with-annotations.jpeg)
The arrows point to 5 skulls. Some of them are obscured by other anatomy in the abdomen. This poor mom needs to have a bowel movement, too!