Home / Practice / Veterinary: pregnancy (cats, dogs)

How a pregnancy ultrasound is done in dogs and cats

A pregnancy scan is one of the most pleasant exams in veterinary practice and one of the most demanding: the breeder wants three answers at once. Is she pregnant, how many puppies or kittens, and when is she due. Ultrasound answers the first question reliably and the other two only approximately, and it is important to explain that well. Here is how the exam goes, what is measured and where the time goes.

What is examined

Fasting is not required, but a full bowel gets in the way, so a planned scan is best done a few hours after a meal. The bitch or queen is placed on her back or side, and the coat on the lower abdomen is clipped or soaked with alcohol; many breeders ask not to clip pregnant bitches, in which case the window is limited to a small area. A 7.5-10 MHz probe suits cats and small dogs, 5 MHz suits large bitches.

Each uterine horn is followed all the way from the cervix to the ovary on each side, slowly and with overlapping sweeps. Every gestational sac is noted, and you try not to come back to it so as not to count it twice. The number of fetuses is recorded as an estimate: the horns fold over each other, and in a large litter ultrasound tends to undercount rather than overcount.

On one or two well-imaged fetuses, the inner chorionic cavity diameter, crown-rump length, biparietal diameter and body diameter are measured. Gestational age is estimated from them using established formulas for medium-sized breeds, with a larger error in small and giant breeds. Heartbeat and movement are checked in every fetus that can be imaged: this is the main sign of viability.

The placentas are described separately (in dogs and cats they are zonary and look like a band around the gestational sac), along with the amount and homogeneity of the fetal fluids and the uterine wall. The scan looks for signs of resorption: a small sac without a heartbeat, with an irregular outline and cloudy content. In mid-pregnancy the ovaries often cannot be seen behind the enlarged uterus, and that is normal.

• Mating date and expected stage
• Uterus: size, horns, wall
• Number of fetuses and count reliability
• Gestational sac, CRL, BPD, body diameter
• Fetal heartbeat and viability
• Gestational age by fetal measurements
• Placentas, fetal fluids, signs of resorption
• Ovaries and other findings

How long it takes

The scan itself takes ten to fifteen minutes, longer with a large litter: careful counting takes the most time. The report is shorter than an abdominal one, but it has a lot of descriptions, and the breeder wants it right away to take home. Typing it by hand adds about eight minutes for entering the data, checking the measurements and wording the gestational age. By voice, the report is ready when the scan ends.

The same study by voice

Species, breed, weight, age and sex of the female go into the study record in advance and are not dictated. The veterinarian describes what they see during the scan: how many fetuses in which horn, measurements, heartbeat, and the values land in their rows. Below is the dictation from a real case: a three-year-old Beagle, bred twice, the first mating thirty-five days ago. Play it in full or click individual lines.

Numbers are recognized with their units and go into the rows of their measurements, and descriptions go into their own fields, not into a block of text. The number of fetuses and the note on count reliability sit side by side, so the document makes it clear right away that six is an estimate, not a promise. The fetal heart rate reference is filled in based on the species in the study record.

The protocol gives a fetal heart rate reference of 200-250 beats per minute in dogs and 220-260 in cats; fetal heart rate is several times higher than the mother's, and a noticeable slowing needs attention. Gestational age by fetal size is counted from ovulation, not from mating, so in a bitch bred several times a difference of a few days is normal. Interpretation always belongs to the veterinarian.

What the finished document looks like

The same data produces the finished documents right away. The table suits the veterinarian for comparison with a follow-up scan closer to whelping, while the narrative version is clearer for the breeder and the owner.

Frequent questions

What it changes on a shift

The breeder leaves with good news and wants to take it home on paper. If the report is built during the scan, it is ready together with the last fetus, and the veterinarian has time to calmly explain why six puppies is an estimate, not a guarantee.

The first 15 reports are free. After that the price depends on the pack size: from 0.42 to 0.53 USD per report, whatever the length of the dictation. No subscription.

App file

Point your phone camera: the download page with the file and its checksum.

Open →

More from practice