The process of placental delivery and the subsequent involution of the uterus during the puerperium are often described as the third and fourth stages of labor. This chapter presents a brief historical review concerning third- and fourth-stage events, followed by a discussion of the physiology of placental separation and uterine involution. The diagnosis and treatment of retained placenta and membranes (secundines), uterine inversion, postpartum hemorrhage and atony, and hematomas are considered. Important cultural and historical events in world history have been directly influenced by complications of involving the third stage of labor. Active management of the third stage of labor consists of the immediate administration of oxytocin after delivery of the infant, early cord clamping, and gentle traction on the cord, combined with gentle uterine massage to prompt placental separation. Periurethral lacerations, which often bleed freely, appear in the thin tissues on either side of the clitoris or urethra.

Magnetic resonance imaging (MRI) with or without contrast is the study of choice when cerebellar, brainstem, or internal auditory meatus pathology is suspected. Similarly, the yield of computed tomography (CT) brain scans is minimal in patients with syncope or near syncope. Suspected spinal cord compression is best defined by MRI. Traumatic or atraumatic myelopathy should be investigated with emergent MRI. In case of nontraumatic myelopathy, the entire spine must be evaluated by MRI. Ready access to CT and its accurate interpretation is essential in evaluating the patient presenting with a new ischemic neurological deficit. Epidural hematomas are often associated with skull fractures, which should be evaluated with CT bone settings and the plain radiography. Most of epidural hematomas result from laceration of the meningeal arteries and/or dural venous sinuses. MRI is particularly sensitive in demonstrating subacute subdural hematomas because of its inherent soft tissue contrast characteristics and its multiplanar capability.