Retrospective Analysis of the Incidence of Retained Placenta in 3 Large Colonies of NHP

During 1999 through 2014, retained placenta was the most common cause of clinical admission for reproductive complications in breeding colonies of baboons (approximate colony size, 2000 animals), cynomolgus macaques (approximately 1000), and rhesus macaques (approximately 500) at the Southwest National Primate Research Center. Retained placentas occurred in 2.7% of baboons, 3.3% of cynomolgus macaques, and 1.0% of rhesus macaques. Apparent risk factors for retained placenta included stillbirth or abortion and at least one prior cesarean section. There was a significant association between stillbirth and retained placenta in all species. Cesarean sections were performed routinely for baboons to meet research objectives but occurred only as needed for cynomolgus and rhesus macaques. Having had at least one prior cesarean section was an incidence factor for retained placenta in 37.0% of baboons and 4.7% of cynomolgus macaques; none of the rhesus macaques with retained placentas had undergone cesarean section previously. More than 90% of dams with retained placenta returned to a successful reproductive life or assignment to a nonbreeding research protocol. Advances in reproductive management will benefit from prospective studies that capture additional data from all members of a breeding group prior to reproductive complications.