Pregnancy and Fetal Development: Cephalic Presentation and Other Descriptive Ultrasonographic Findings from Clinically Healthy Bottlenose Dolphins (Tursiops truncatus) under Human Care

SIMPLE SUMMARY: Ultrasound data are vital for monitoring and detecting problems in pregnancies, and although there is a significant amount of data for domestic species, data for marine mammals are scarce. In domestic species, the use of ultrasonography to monitor a pregnancy usually has the following aims: fetal movements, fetal heart rates, measurements of the skull and the thorax for the prediction of the birth date interval, the morphological aspects of the fetal organs, the appearance of the umbilical cord, and the placentation. The purpose of this study is to provide to the clinician additional relevant data on fetal development and well-being during a dolphin pregnancy that may also be useful for wild population monitoring. This study is the result of a retrospective analysis of 192 ultrasound scans over 10 years that, for the first time, describes the sonographic findings of the bottlenose dolphin organogenesis and their correlation with the stage of pregnancy, as well as the calf presentation at birth, according to its position within the uterus, and moreover a complete literature review. ABSTRACT: Ultrasonography is widely used in veterinary medicine for the diagnosis of pregnancy, and can also be used to monitor abnormal pregnancies, embryonic resorption, or fetal abortion. Ultrasonography plays an important role in modern-day cetacean preventative medicine because it is a non-invasive technique, it is safe for both patient and operator, and it can be performed routinely using trained responses that enable medical procedures. Reproductive success is an important aspect of dolphin population health, as it is an indicator of the future trajectory of the population. The aim of this study is to provide additional relevant data on feto-maternal ultrasonographic monitoring in bottlenose dolphin (Tursiops truncatus) species, for both the clinicians and for in situ population studies. From 2009 to 2019, serial ultrasonographic exams of 11 healthy bottlenose dolphin females kept under human care were evaluated over the course of 16 pregnancies. A total of 192 ultrasound exams were included in the study. For the first time, the sonographic findings of the bottlenose dolphin organogenesis and their correlation with the stage of pregnancy are described. Furthermore, this is the first report that forecasts the cephalic presentation of the calf at birth, according to its position within the uterus.