Retained placenta occurs when the placenta is not expelled from the uterus within 30 minutes of childbirth. Risk factors include previous retained placenta, uterine injuries or surgery, preterm birth, and induced labor or multiple pregnancies. Causes can be failure of the placenta to separate fully, simple adherent placenta, or morbid adherence where the placenta burrows deeply into the uterine wall. Management involves emptying the bladder, nipple stimulation, controlled cord traction to remove the placenta, or potential manual removal in theater or hysterectomy if deeply embedded. Complications can include uterine inversion, hemorrhage, sepsis, or hysterectomy.