The lack of involution of the uterus following childbirth, manifested by a large uterus (greater than 100 g) and a continuation of lochia rubra beyond the usual time. It is caused usually by puerperal infection, overdistention of the uterus by multiple pregnancy or polyhydramnios, lack of lactation, malposition of the uterus, and retained secundines. Involution is aided by the certainty that the placenta is intact at the time of delivery and the use of ecbolics to cause uterine contraction.