**1. Introduction**

Ectopic pregnancy is a major public health problem worldwide. The incidence of ectopic pregnancy (EP) has been increasing recently. Currently, approximately up to 2% of pregnancies are ectopic (CDC, 1995). It is a leading cause of mortality in the first trimester of pregnancy (Berger et al., 2003). Furthermore, it is an important cause of morbidity and a high percentage of these patients may become infertile. For all these reasons efforts should be made to perform an early diagnosis before the occurrence of rupture. However, there can be misdiagnosis because the clinical presentation of ectopic pregnancy can simulate a variety of other pelvic diseases. Therefore, the physician must keep a high index of suspicion. Diagnosis has improved with the evaluation of the levels of beta-human choriongonadotropin hormone (beta-hCG) and through transvaginal ultrasound. Consequently, ectopic pregnancies can often be diagnosed before the patient's condition has deteriorated, which has changed the former clinical picture of a life-threatening disease into a more benign condition in frequently asymptomatic patients. As a result, early detection through non-invasive diagnosis makes it possible to perform conservative treatment, such as expectant management or medical treatment with methotrexate (MTX).

Additionally, atypical localization of ectopic pregnancies is associated with greater morbidity. In these situations medical treatment with systemic MTX and in cases with embryonic cardiac activity treatment with direct injection of potassium chloride or MTX has been used effectively. Clinical treatment avoids surgeries such as hysterectomy that end up being required in great number of cases of unusual localization.

In this chapter, it will be discussed aspects related to the conservative treatment of ectopic pregnancy, mainly clinical treatment with expectant management and medical treatment of methotrexate. The chapter will point out features of the selection criteria, methotrexate protocols, predictive factors of success and reproductive future.
