Pregnancy Diagnosis - X-rays v ultrasound

A tricolour young female Pom X looking like a minature Sheltie was mated by a male Poodle.
One lateral X-ray view of the Pom's abdomen is sufficient. The ultrasound scan is an alternative if the owner is worried about radiation to the puppies. However, one X-ray is not known to harm the puppies. In ultrasound scan, much depends on the expertise of the vet interpreting the scan. Some vets cannot ascertain the number of puppies when there are multiple ones and would give a report as "four or five" puppies. For the X-ray, the number of spinal columns will show clearly. In this case, there are 2 and therefore 2 puppies.