Canine Pregnancy Diagnosis


p 73-77


Abdominal Palpation

  • If the bitch is at a stage of gestation which enables it, abdominal palpation can be used to diagnose pregnancy. 

  • Some skill and care are required to adequately perform uterine palpation in the pregnant bitch.


  •  It is usually best to use one hand to palpate most dogs. 

  • The abdomen is palpated from the hepaxial muscles downward, attempting to slip the uterus between the thumb and fingers. 

  • In smaller dogs, one finger can be placed in the rectum and used as a landmark for palpation.  

  • The non-pregnant uterus and the pregnant uterus before day 21 of diestrus is not reliably palpated in most dogs.

A contrast radiograph of a bitch's uterus in estrus
demonstrating how small it is. The faint black arrow is the cervix.

  • During pregnancy however, from day 21 to day 31 from the first day of diestrus, when the uterus slips between your thumb and fingers you can fell 'walnuts', which are the distinct gestational vesicles. 

  • These vesicles average 1.5-3.5 cm between days 28-32 of pregnancy.

Click on the movie icon, then right click on the movie or "Open It" and "OK" to see
Canine Abdominal Palpation

A photo showing the distinct gestational sacs.

A photo showing how the gestational sacs become confluent,
and therefore difficult to distinguish.

  • It is difficult to accurately count the number of fetuses and the viability of the pregnancy cannot be determined by abdominal palpation.  

  • Some dogs are too large to palpate and some tense the abdomen and make palpation very difficult. 

  • Some dogs carry the pregnancy more cranial, therefore making palpation more difficult. 

  • Mammary enlargement may also make palpation difficult. On very large dogs, you may try to palpate with two hands, but it is not the best way to palpate. 

  • After day 31 the gestational sacs become more confluent and lose their distinction. However, after day 50 the puppies may be palpated directly.


  • (Yeager et. al. AJVR 53, 1992)  

    • Gestational sacs are visible as early as 18-20 days past the LH peak. 

    • There is usually little doubt when the black, hyperechoic gestation sac is observed, that the bitch is pregnant.  

  • Ultrasound is more accurate than palpation at all stages than palpation or radiography. 

  • The presence of fetal heartbeat and fetal movement can accurately establish fetal viability. 

    • The heartbeat is normally first seen more than 23- 25d after the LH peak. Fetal movement is seen after day 34-36 past LH peak 28.

  • Predicting gestation duration from ultrasound measurements

  Less than 40 days More than 40 days
Gestational Sac Diameter

(GSD) cm


GA = (6 X GSD) + 20

GA = (15 X HD) + 20


Crown-Rump Length

(CRL) cm

GA = (3 X CRL) + 27


Head diameter

HD (cm)


GA = (15 X HD) + 20



Ultrasound Sector Scan of Canine Pregnancy at 25 days.

Click to see the structures identified.

Click on the movie icons below to see ultrasound videos.

Ultrasound 25 days

Ultrasound 49 days

Ultrasound 52 days

Ultrasound 55 days




  • Ultrasound is especially useful between days d 33-45, because it is too late to palpate and too early for radiographs. 

  • Counting the number of fetuses difficult, because you can never be sure if you are seeing another fetus when you move the probe, or if it is the same one. 

  • Small litters may make it more difficult for ultrasound to be used to diagnose pregnancy. 

  • Ultrasound has great value in obstetrical use in the determination of fetal viability. 

    • The normal heart rate in the fetus is 200 beats per minute. 

    • An increase or decrease in the fetal heart rate indicates fetal stress. 

    • The absence of a heartbeat indicates fetal death.



  • The fetal skeleton becomes opaque 43-46 days after the LH peak making radiographic diagnosis of pregnancy possible 45-48 d after LH peak. 

  • Bones become visible at different times (see Rendano, Current Veterinary Therapy VIII, Kirk, ed.); for example, teeth are visible approximately 4 d before birth.  

  • After 50 days you can count the number, estimate size, and estimate the position of fetuses.

  • At LSU we routinely do a radiographic 'puppy count' to determine how many pups there are. 

    • This makes the attendant at whelping much more aware if whelping is done, or if assistance is needed. 

    • No negative effects have been seen in fetuses that were radiographed during the latter stages of gestation. 

  • Fetal Death Signs of fetal death can be visible to the trained eye.  

    • An alteration of fetal skull bone alignment with overriding or extreme deformity is a sign of fetal death. 

    • Intra- or peri- fetal gas accumulations indicates fetal death.  

    • Abnormal fetal posture such as the "ball sign" which is the increased flexion or straightening of hind limbs.

Can you see the pregnancy in this radiograph? No one can. The bitch is pregnant, however the uterine enlargement which is visible cannot be definitively diagnosed as a pregnancy. It may be a pyometra.

On this radiograph the fetal skeletons are actually visible. .


(Click on the image to see a larger picture)


  • Relaxin is first observed at 20-30 d gestation and is present for 30-60 d postpartum.  

  • A test is marketed by Symbiotics - ReproCHEK  

  • The test seems good, but you must buy 16-40 tests (depending on how many you run at once) for $240 (one year shelf life). If you only test dogs occasionally, then the price is pretty about ultrasound.

  • Witness Relaxin

    • 5 Tests/box

    • Room temperature storage

    • 10 minute running time

    • Cost $78/5 tests


Acute phase proteins

  •   Acute phase proteins are present 28-37 days after the last breeding. 

  • A company (ICAGEN) marketed a mail in kit that claimed 95% accuracy, however the test is unavailable at this time.


contributed by Bruce E Eilts on 22 July 2006

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contributed by Bruce E Eilts on 25 September 2012


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