Duration of the third stage of labor in a female yellow baboon from Mikumi National Park, Tanzania.

In human obstetrical practice, placental retention is defined as failure of placental expulsion within 45 min of fetal delivery, and is of concern given the potential for hemorrhage or infection. Because of the difficulty in observing the parturition event, few data exist on variation in the duration of this stage of labor in free-ranging primates. In Mikumi National Park in Tanzania we recorded an interval in excess of 2 h between delivery of the infant and expulsion of the placenta in a yellow baboon (Papio cynocephalus). This observation is a significant addition to our knowledge of normal parturition in the wild.