Ultrasonographic findings associated with normal pregnancy and fetal well‐being in the bottlenose dolphin (Tursiops truncatus)

Abstract

Reproductive success is vital in sustaining free‐ranging and managed bottlenose dolphin (Tursiops truncatus) populations. Ultrasonography is an invaluable, non‐invasive tool in assessing the fetomaternal unit in humans and animals, including dolphins and horses. The purpose of this prospective longitudinal cohort study was to develop a protocol for fetomaternal ultrasonographic monitoring in dolphins and to report normal measurements and descriptive findings correlated with a positive outcome. From 2010 to 2017, serial ultrasonographic evaluations of 12 healthy dolphins were performed over the course of 16 pregnancies. A total of 203 ultrasound examinations were included in the study. Several metrics were accurate in predicting fetal age. Fetal biparietal diameter (BPD), thoracic width in dorsal and transverse planes, thoracic height in a sagittal plane, aortic diameter, and blubber thickness all demonstrated high correlation with gestational age (r > 0.94, P < .00001). Regional uteroplacental thickness significantly increased with each trimester (range 0.22–0.40 cm; P < .00011 cranial uterus, P < .00057 mid, and P < .000011 caudal). Lung:liver mean pixel intensity was 2.57 ± 0.46 (95% confidence interval 2.47‐2.67). Ultrasonographic characteristics of normal pregnancy in dolphins are described and an equation for prediction of parturition date in Tursiops is reported: days to parturition = 348.16 − (26.03 × BPD(cm)) (R2 = 0.99). Future applications of these normal data will help identify in utero abnormalities indicative of fetal morbidity, and improve understanding of reproductive failure in wild and managed populations.

Embryo and fetal position during pregnancy by ultrasonographic examinations in bottlenose dolphin (<i>Tursiops truncatus</i>)

“…In the present study, snout of fetus is always at the top of uterine horn, while tail lies close to the cervix after 90 days pre-partum . Its position was similar to the illustrations of fetomaternal anatomical structure in third trimester [ 9 ] and the detailed drawing by Wislocki and Enders [ 22 ], however, the present fetal position ( Fig. 5A ) is similar to the detailed drawing [ 22 ], which is closer to dam’s body wall than the illustrations [ 9 ].…”

“…Ultrasonography is a valuable non-invasive diagnostic tool on small cetaceans in general, especially pregnancy in bottlenose dolphins is best diagnosed with ultrasonography [ 7 ]. Ultrasonography has been used for early pregnancy diagnosis in dolphins, and in most cases measures ovary [ 3 , 12 ], the size of follicles before ovulation [ 13 ], size of embryo [ 16 ] and fetus, fetal heart beat and movement [ 16 , 21 ], as well as the diameter of the fetal head and thorax [ 9 , 10 , 21 ].…”

“…In cetaceans, few of the fetomaternal anatomical structures during pregnancy by ultrasonography has been reported [ 9 ]. Furthermore, there are few manuscripts which describes how a fetal position will be within the birth canal at parturition [ 16 ].…”

Comparisons of Serum Progesterone and Progestagen Concentrations in Normal and Abnormal Bottlenose Dolphin (Tursiops truncatus) Pregnancies

“…Furthermore, historically inaccurate identification of conception dates or data collection at birth impedes evaluation using obvious factors, such as gestation length, length of labor and calf birth weight, as potential risk-increasing identifiers of perinatal mortality in bottlenose dolphins. As techniques for monitoring reproductive activity (Robeck et al, 2013), gestational development (Ivancić et al, 2020), and early calf development (Sweeney et al, 2010) are integrated into bottlenose dolphin reproductive management programs, and as more data is collected under these conditions, future research should be conducted to evaluate risk factors on bottlenose dolphin neonatal mortality.…”

Impacts of Petroleum, Petroleum Components, and Dispersants on Organisms and Populations

“…Chronic maternal illness in the aftermath of the DWH oil spill is the likely cause of reproductive failure. Normal progression of fetal development in utero (Barratclough et al, 2020;Ivančić et al, 2020) and retrospective examination of pregnancies with known failed outcomes have enabled several hypotheses as to the potential mechanisms of pregnancy failure, with maternal illness standing out unequivocally as the most important predictor for pregnancy complications (Smith et al, 2020). Various data were integrated with the complete veterinary case history for each dam (female) and the resulting fetal and placental histopathology findings to elucidate maternal, placental, and fetal predictors of pregnancy failure.…”