The diagnosis of pregnancy can be made by palpation, measurement of the hormone relaxin, ultrasonography, or radiography. Abdominal palpation for pregnancy is best performed between 21 and 28 days, when the fetal vesicles can be felt like small "golf balls." Tense, obese, and heavily muscled bitches are more difficult to assess. This technique does not allow determination of fetal viability or number.

Relaxin is a pregnancy – specific hormone that can be easily measured by a simple blood test any time after 28 days. Like palpation, this only confirms pregnancy, not fetal viability or numbers.

Ultrasonography can identify fetal vesicles as early as 17 days gestation. More reliable identification of gestational sacs is obtained at 25 to 30 days from the last breeding or 22 – 28 days after the LH peak. Fetal movement and heartbeats can be seen at 28 days gestation. The presence of intestinal gas can interfere with observation of fetal sacs. While sonographic pregnancy diagnosis is 97% accurate at 30 days of gestation, the accuracy for fetal number is only 37%. This technique has the advantage of allowing assessment of fetal health. It can also be used to help predict the date of whelping in cases where the date of ovulation is not known.

Radiography can identify fetal skeletons at after 45 days of gestation. Due to the potential disparity between days from breeding and gestational age, radiography at or after 50 days from last breeding is recommended to prevent false negative results. Ideally, the bitch will be radiographed with an empty stomach and colon to enhance the ability to observe all fetuses present. Evaluation of both lateral and ventrodorsal views is essential. In most cases, these parameters will allow an accurate count of pups present. Radiography is relatively insensitive in identifying fetal distress, as fetuses must be dead for at least 24 hours before radiographic signs are present. This technique is also helpful in determining the size of the pups relative to the dam’s pelvis, and to check for retained puppies after whelping has occurred.

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References: Portions of this article were taken from these articles:

Freshman, Joni L. Dvm, MS, DACVIM. The Dam's The Thing: Care Of The Pregnant Bitch. Veterinary Information Network, Inc. www.veterinarypartner.com.

Birthing Puppies. VeterinaryPartner.com. Veterinary Information Network, Inc. www.veterinarypartner.com