Scientists at the National Marine Mammal Foundation have developed the most advanced ultrasound technique yet for dolphins, whales, porpoises and other small cetaceans in managed environments, as well as those living in the wild. The technique allows veterinarians to diagnose problems as early as the first trimester of pregnancy in dolphins—giving researchers a chance to save the pregnancy.
To develop the technique, veterinarians followed 16 healthy pregnancies of dolphins in human care and, using 203 ultrasound examinations, determined normal findings for both the fetus and placenta. The study, published in Veterinary Radiology & Ultrasound, sets a standard ultrasound pregnancy protocol with normal measurements over time, giving veterinarians a more advanced technique for marine mammal assessments.
“From this analysis we determined several metrics were accurate in predicting fetal age, including skull size, width and height of the chest, aortic diameter, and blubber thickness,” Forrest Gomez, NMMF's Director of Medicine and co-author of the study, told Laboratory Equipment. “We also found it was normal for the thickness of the uterus and placenta to increase significantly with each trimester. This is an important finding as placental infection and abnormalities can be a cause of pregnancy failure in dolphins.”
The new non-invasive fetomaternal ultrasonographic technique can be performed in minutes, which is especially important for wild populations. The researchers say even a single ultrasound from the entire pregnancy of a wild dolphin is valuable, affording them a better understanding of reproductive health within specific groups.
This work was part of an investigation into the long-term health effects of the Deepwater Horizon oil spill. From a wild dolphin perspective, a better understanding of reproductive failure provides insight to the potential short- and long-term impacts of environmental disasters and human activity.
“Environmental disasters affect wildlife and the environment in different ways, many of which are not well understood,” Gomez said. “The Deepwater Horizon spill caused a major reduction in pregnancy success in bottlenose dolphins living within the oil spill footprint. Being able to investigate possible causes of reproductive failure in these dolphins gives scientists clues as to how oil is impacting female dolphin health and the overall reproductive rate of the resident population.”
When developing the new technique, researchers looked to mimic human medicine as the gold standard for fetal ultrasounds. Additionally, since dolphins have the same type of placenta as horses, the researchers incorporated current practices in equine medicine throughout their cetacean technique development.
The NMMF researchers recently released a second study reporting the normal reference intervals for blood analyte levels according to trimester in healthy pregnancies in managed dolphins.
“This will allow for more accurate interpretation of blood sample results in managed pregnant animals to prevent over or underdiagnosing abnormalities and administering unnecessary treatments,” the researchers wrote in the study. “While these are not directly applicable to wild counterparts, the [results] described provide a basis for comparative use in maternal health assessment.”
Photo credit: NMMF