When to X-Ray

• The skull and spine of puppies become visible on X-rays about 42 days after conception. According to the University of Missouri Extension office, fetuses that have developed less than 42 days will not show bone development and will look much like the intestines of the dog.
  
  

Reasons to X-Ray

• The X-ray can be used to confirm pregnancy but also to ascertain the number of puppies. The number of skulls is usually counted. This is useful when a difficult delivery is anticipated. If the number of puppies is known, the dog owner can take steps if the dog is not able to deliver all the puppies naturally.
  
  

Other Reasons to X-Ray

• The veterinarian will also check the X-ray for any signs of abnormality in the pregnancy. This can include enlarged organs or fluid accumulations. This becomes another step in confirming the health of the female dog during the pregnancy.
  
  

X-Rays and C-Sections

• Some breeds of dogs are customarily delivered by Cesarean section. X-rays are commonly used to determine how far the puppies have developed. The veterinarian will look for the development of fetal teeth indicating the puppies have developed at least 56 days from conception.
  
  

Early Tests

• An ultrasonic exam can detect fetuses as early as 15 days after conception. Manual palpation can detect the puppies after about 4 weeks. X-rays, while the most reliable of these methods, is not useful until about 42 to 45 days after the mating.