Adenomyosis of the uterus is a serious problem for women of reproductive age because of its possible consequence of infertility. We present the case of a woman who had adenomyosis of the uterus, a successful spontaneous pregnancy, and delayed and tenacious postpartum hemorrhage that did not respond to conservative treatment. The 26-year-old woman, gravida 1, para 1, suffered from fulminating vaginal bleeding and associated shock 20 days after the delivery of a 3,450-g female by Cesarean section. Conservative treatment included uterine compression and massage, blood transfusion, intravenous administration of high-dosage estrogen, oxytocin and sulprostone (prostaglandin E analogue), and gauze packing from the vagina into the uterine cavity. Despite treatment, the patient went into shock due to persistent vaginal bleeding. Emergency exploratoric assessment laparotomy was performed, followed by a stotal hysterectomy. Pathology revealed extensive adenomyosis of the uterus without other significant abnormality. The potential dangers of adenomyosis in pregnancy should not be overlooked when patients seek treatment for infertility.