CHAPTER 51 ■ OLIGOMENORRHEA SARAH C CAVALLARO, JEANNINE DEL PIZZO, MARY L SCHUCKER INTRODUCTION Oligomenorrhea, or infrequent menstrual bleeding, can usually be evaluated and managed in the outpatient setting The pediatric emergency physician should be familiar with the common causes of oligomenorrhea with focus on those causing true medical emergencies This chapter will focus the adolescent presenting with oligomenorrhea and the recognition of acute or life-threatening causes and provide recommendations for patients who can be safely cared in the outpatient setting DEFINITIONS Although this chapter will focus on the approach to an adolescent with infrequent menstrual bleeding, the term “oligomenorrhea” is no longer used by the FIGO World Congress of Gynecology and Obstetrics nor by the American College of Obstetricians and Gynecologists For the pediatric emergency physician , oligomenorrhea can be defined as an interval of more than weeks between two menstrual periods The newly accepted term of infrequent menstrual bleeding refers to one to two episodes of menstrual bleeding in a 90-day period If menstrual cycles not resume within to months, the term secondary amenorrhea is applied Some patients with anovulatory menstrual cycles have oligomenorrhea punctuated by episodes of excessive bleeding An approach to the evaluation of abnormal vaginal bleeding is presented in Chapter 79 Vaginal Bleeding This chapter will not specifically discuss primary amenorrhea—that is, failure to menstruate by a specified age, often 16 years However, some disorders discussed here that cause secondary amenorrhea, may also cause primary amenorrhea as part of an overall delay in pubertal development DIFFERENTIAL DIAGNOSIS The differential diagnosis of oligomenorrhea is given in Table 51.1 EVALUATION AND DECISION History