Abstract

Congenital postural deformities secondary to intrauterine molding are prevalent and have been well described in humans. Intrauterine molding can be caused by intrinsic neuromuscular disease or malformation, and more commonly extrinsic factors related with primiparity, maternal hypertension, placental dysfunction, and low amniotic fluid. The presence of compressing masses, twin pregnancy, and certain fetal presentations have also been correlated with an increase in incidence of deformities.¹

Head-first births are not common in Tursiops species,^2,3 as such, there are not many detailed reported cases published in available literature. They are considered a natural variation of fetal positioning.³ The objective of this case report is to describe a rare complication observed from an abnormal fetal position in-utero associated with a head-first presentation, and to reinforce the need of comprehensive pre- and post-labor management protocols in cetacean species.

A 19-year-old primiparous Indo-Pacific bottlenose dolphin (Tursiops aduncus) female gave birth to a head-first female calf in May 2019. Throughout gestation, the fetus was routinely assessed via ultrasound. Fetal growth was considered normal, but fetal position was observed to be inverted, indicating a head-first presentation and with an abnormal medial positioning of the fluke. No other major abnormalities were observed. Labor was initially normal with beak visualization at the level of the genital slit. During progression, the calf beak retracted and appeared to lodge caudally within the dam’s genital slit. Despite active contractions from the dam, labor started to delay and showed no progression. The fetus was manually repositioned with the dam’s cooperation, and the beak was again fully exposed after two interventions. Labor started to progress again, and the calf was delivered without further assistance. The calf presented with a tail malformation and inability to surface. After transferring the calf to a medical pool, a physical evaluation including blood sampling and radiographs were performed. No major skeletal abnormalities were noted, but the distal peduncle was curved dorsally with the fluke bending to the left. The postural deformity was attributed to possible muscle atrophy, due to abnormal in-utero positioning, among other factors. Feeding by gavage was initiated, and active postural assistance with supportive swimming were provided. The calf started to decline after 30 hours and despite medical intervention, her condition continued deteriorating and eventually expired at 38 hours post-partum.

This case describes the clinical findings pre- and post-labor in a calf with a congenital postural deformity after a head-first birth. It supports the importance of having comprehensive pregnancy protocols in place, and their relevance in the early diagnoses of complications. Despite head-first deliveries not being considered pathologic,^3,4 their association with complications has been documented,^5,6 and medical plans for neonatal support should be prepared in advance to provide efficient response and maximize neonatal survival.

Acknowledgements

The authors wish to thank Marine Mammal Operations, Atlantis Dubai, for all their efforts in the preparation and difficult handling of this case. The close animal relationship and trust between trainers and animals made intervention possible and minimized traumatic intervention during labor. Also, a special thank you to Heidi Pérez Cao for being available to guide and support the team during the calving season of 2019.

*Presenting author

Literature Cited

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2.  Robeck TR, O’Brien JK, Atkinson S. 2018. Reproduction. In: Gulland FMD, Dierauf LA, Whitman KL, editors. CRC handbook of marine mammal medicine. 3rd ed. Boca Raton (FL): CRC Press. p169–199.

3.  Saviano P, Fiorucci L, Grande F, Macrelli R, Troisi A, Polisca A, Orlandi R. Pregnancy and fetal development: cephalic presentation and other descriptive ultrasonographic findings from clinically healthy bottlenose dolphins (Tursiops truncatus) under human care. Animals [Internet]. 2020 [cited 2020 December 20];10(5):908. Available from: doi:10.3390/ani10050908.

4.  Deng X, Hao Y, Serres A, Wang K, Wang D. 2019. Position at birth and possible effects on calf survival in finless porpoises (Neophocaena asiaeorientalis). Aquat Mamm 45(4):411–418.

5.  Larson KM, Martelli PR, Lee FK, Fernando NM. 2012. Multiple birth defects in a captive-born 10-day-old Indo-Pacific bottlenose dolphin (Tursiops aduncus) with a likely association to a head-first presentation at parturition. IAAAM 43rd Annual Conference Proceedings, Atlanta, GA.

6.  Đuras-Gomerčić M, Gomerčić T, Galov, A, Lucić H, Škrtić D, Ćurković S, Vuković S, Gomerčić H. 2010. Difficult labours with fatal consequences in bottlenose dolphins (Tursiops truncatus) from the Adriatic Sea. 24th Conference of the European Cetacean Society, Stralsund, Germany; Pp. 269.