Editor’s note: Second in an ultrasound series
Just as a live calf can make the dairy money, a dead fetus that goes undetected for various lengths of time can be costly in a variety of ways. One way to identify a dead fetus as early as possible is through ultrasound.
“Have you ever walked into a barn very early in the morning, looked at a cow and you know she is dead? The same is true of bovine ultrasound,” states Craig DeMuth, DVM, Truxton, N.Y. “You know the cow is dead because she is not moving or breathing. With ultrasound you know the fetus is dead because it is not moving and there is no heartbeat.”
“The diagnosis of fetal death is one of the significant advantages of bovine reproductive ultrasound versus rectal palpation,” adds DeMuth.
Dead fetuses commonly palpate like live fetuses, and may not be expelled for extended periods of time. “My experience has been that some cows will not expel dead fetuses for months,” explains DeMuth. “This causes cows not to become pregnant when they should be pregnant, and when this occurs, there is always loss of profit. In some cases this may be life threatening. If a cow does not become pregnant within a period of time to maintain profitability, she is culled.”
Early fetal death detection
“Ultrasound can detect fetal death as early as ultrasound can detect fetal life,” says DeMuth. “Heartbeat is one of the earliest signs of life in the fetus and this can be detected by ultrasound as early as 19 days, under perfect conditions and with a highly proficient ultrasonographer.” Ultrasound can detect fetal death earlier than rectal palpation.
Ultrasound is a very dynamic diagnostic tool, notes Jill Colloton, Bovine Services, LLC, Edgar, Wis. “It is live frame. Even before scanning the fetus, an experienced ultrasonographer will scan abnormalities in fetal fluids and fetal membranes. Increased flocculation in fetal fluids and separation of fetal membranes are not normal in early stage fetuses.”
Colloton feels comfortable calling a fetus dead between 26-55 days if she has at least two “cardinal signs” of fetal death. Those cardinal signs of fetal death prior to 55 days are lack of fetal heartbeat, flocculation in the amniotic or chorioallantoic fluid and separation of the chorioallantois from the uterine wall (it appears to “float”). “After 55 days it’s normal for flocculation of the pregnancy fluids to develop and for the membranes to fold and ‘float’, but at that stage the presence or absence of fetal movement and heartbeat will be easy to detect in viable fetuses,” says Colloton.
DeMuth says the more important question is when can the scanner be 100% confident that the fetus is dead? “The answer to that question is the same as the stage at which ultrasound can determine pregnant or open in the bovine. A proficient scanner can accurately determine pregnant or open at day-27 of gestation.”
DeMuth notes that the fetus is best visualized when isolated in fetal fluids. Prior to day-27 and depending on environmental conditions, there may not be enough fetal fluids to accurately identify the fetus.
Once a fetus is determined not to be viable, it should be expelled using prostaglandin. When the corpus luteum regresses, the fetus will usually be fully expelled within days. In most pregnancies less than 90 days, the cow will be clean enough to re-breed within two weeks of the prostaglandin injection. Colloton adds that mummies do not expel as readily, but they are not usually seen until later in gestation.
Depending on unit quality, ultrasound is definitely capable of detecting fetal abnormalities. This raises one of the very fundamental questions about unit purchase. A unit must be purchased that has enough resolution to be capable of the desired diagnostics. For instance, heart rate is high in 30-day fetuses — about 130 beats per minute. “Slower heart rates in these young fetuses are abnormal, and can be indicative of bad things to come,” explains DeMuth. “These fetuses may be close to death or have abnormalities.”
An experienced ultrasonographer may get a gut feeling that something is wrong as early as 30 days, but it’s easiest to identify fetal abnormalities at the recheck exam after 55 days, adds Colloton. At that stage the fetus should look like a tiny version of a calf. Schistosomus reflexus, fetal hydrops, Siamese twins and badly deformed limbs are usually easy to detect at this stage. More subtle abnormalities like arthrogryposis or hydrocephalus are more difficult. “Unfortunately, freemartins are impossible to identify with ultrasound,” says Colloton. “The female genital tubercle becomes the clitoris. The clitoris is usually well-developed in freemartins.”
Very early after incorporating ultrasound into his practice, DeMuth looked at a 39-day fetus. “I could not tell exactly what I thought was abnormal, but the entire fetus did not look normal,” he recalls. “But 28 days later, I was able to diagnose the fetus as a schistosomaous reflexus.” Generally speaking, the fetus is fully developed and normal anatomy is easy to scan by 60 days in gestation. “Sixty days is an excellent time for fetal sexing and also to scan for fetal abnormalities,” DeMuth adds.
What’s it worth to find a dead or abnormal fetus as early as possible? That depends on one’s opinion of the cost of days open. “Without intervention, a dead pregnancy can remain in the uterus for weeks and still have palpable signs of a normal pregnancy,” Colloton says. “Ultrasound can reduce the time to diagnosis considerably, reducing days open and reproductive cull rate.”
Next: Diagnosing twins and fetal sexing