How Ultrasound and X-Ray Are Used During Canine Pregnancy

Ultrasound and X-Ray in Canine Pregnancy

Learn how ultrasound and x-ray are used during dog pregnancy, what each test shows, and when breeders should use them.

Modern veterinary imaging plays an important role in responsible dog breeding. Ultrasound and x-ray are the two main tools used during canine pregnancy, each with a different purpose and ideal timing. Understanding how and when these tests are used helps breeders make informed decisions and avoid relying on guesswork.

This guide explains both imaging methods in clear, practical terms.

Why Imaging Matters in Dog Pregnancy

Hands-on checks and visible belly size can be misleading. Imaging allows breeders and vets to:

• Confirm pregnancy
• Assess foetal development
• Estimate litter size
• Plan for safe whelping

No single method provides all the answers, which is why ultrasound and x-ray are often used at different stages.

Ultrasound in Canine Pregnancy

When Ultrasound Is Used

Ultrasound is typically performed from day 25 to day 35 of pregnancy onward. It is most useful in early to mid-pregnancy.

What Ultrasound Can Show

• Confirmation of pregnancy
• Foetal heartbeats and viability
• Early foetal development
• Uterine health

Ultrasound is the best tool for checking whether puppies are alive, especially if foetal distress is suspected.

Limitations of Ultrasound

Ultrasound cannot reliably:

• Count exact litter numbers
• Assess puppy size near term
• Determine if puppies will fit through the birth canal

As pregnancy progresses and puppies grow, overlapping structures can make images harder to interpret.

X-Ray in Canine Pregnancy

When X-Ray Is Used

X-rays are generally performed after day 55, once puppy skeletons have mineralised.

What X-Ray Can Show

• Number of puppies
• Size and position of each puppy
• Skull and spine development
• Potential risk of difficult labour

X-ray is the most accurate way to determine how many puppies to expect at whelping.

Limitations of X-Ray

X-rays do not:

• Confirm foetal heartbeats
• Detect foetal distress
• Assess soft tissue health

For this reason, x-rays are often paired with ultrasound when there are concerns.

Is Imaging Safe for Pregnant Bitches?

Yes, when performed appropriately by a veterinarian.

• Ultrasound uses sound waves and carries no radiation risk
• Modern x-rays use very low radiation doses and are considered safe late in pregnancy

Vets always weigh the benefit of information against any potential risk.

Choosing the Right Test at the Right Time

Early pregnancy: Ultrasound
Mid-pregnancy concerns: Ultrasound
Late pregnancy and pre-whelping planning: X-ray
Suspected foetal distress: Ultrasound, sometimes alongside x-ray

Your vet will recommend the most appropriate option based on timing and clinical signs.

How Imaging Helps Breeders Prepare

Imaging results help breeders:

• Plan the whelping environment
• Prepare appropriate Whelping Supplies
  
• Organise Heating & Critical Care equipment
• Reduce the risk of retained puppies or delayed intervention

Good preparation supports smoother, safer whelping.

When to Contact Your Vet

Seek veterinary advice if:

• Foetal movement is reduced or absent
• The bitch appears unwell
• Labour does not progress as expected

Imaging is a diagnostic tool, not a replacement for veterinary care.

Final Thoughts

Ultrasound and x-ray each play a vital role during canine pregnancy. Ultrasound confirms life and early development, while x-ray provides critical information for late pregnancy and whelping planning. Used together at the right times, they give breeders clarity, confidence, and the ability to act quickly when something isn’t right. 

Acknowledgement

We would like to thank Magnar Cavalier King Charles Spaniels for allowing us to use the depicted X-ray for our BLOG post and acknowledge the Cooinda Vet Hospital for taking the X-ray.