[Observation of course of placental separation by continuous dynamic ultrasonography during third stage of labor].

Objective: To investigate the physiologic course of third stage of labor, and to judge the optimal time of natural placental separation permitted.

Methods: To observe and record the course of third stage of labor by continuous dynamic ultrasonography and to estimate the total amount of blood loss from placental separation within two hours after delivery by the method of weighing lost blood.

Results: Third stage of labor can be divided into four phases: the latent phase (4.