results support the concept that circulating concentrations ofrelaxin are reduced in association with pregnancy loss regardless if embryo/fetal deaths occur in utero or at birth in bottlenose dolphins. In conclusion, the results of the present study provided new information on the pregnancy-specific nature of relaxin, critical evaluation of the fundamental characteristics of relaxin during pregnancy and pregnancy loss, and clarification on the strengths and limitations of relaxin as a diagnostic aid to determine pregnancy status and assess maternal–fetal health in bottlenose dolphins. AcknowledgmentsThe authors want to thank Dr. Mohd Beg for his contribution to the statistical analysis and individuals in the animal care and veterinary departments at SeaWorld Parks and Entertainment in San Diego, CA; San Antonio, TX; Orlando, FL, USA for their and contribution in collecting blood and processing and archiving serum samples. We also thank Mr. Brad Andrews for his support of this project which was funded by SeaWorld Parks and Entertainment (SEAS) – technical contribution 2015-15-C. This project was also supported by a NYU NIEHS Center Grant ES000260.