Ectopic pregnancy is a common term for what is known as a displaced pregnancy; that is, a condition where the fertilized egg implants outside of the uterine cavity. Therefore, ectopic pregnancy and intrauterine pregnancy are different. In the early stages of an ectopic pregnancy, if there is no splitting of the pregnancy sac or bleeding, there generally are no symptoms. However, the condition can be understood and assessed through some auxiliary examinations. For example, after the cessation of menstruation, an ectopic pregnancy might be accompanied by a small amount of vaginal bleeding, and blood tests for HCG might show that the HCG levels do not double as expected. Or, at a certain gestational week, such as six or seven weeks, an ultrasound might not reveal a pregnancy sac. These are all precursors to an ectopic pregnancy, and if these signs appear, the likelihood of an ectopic pregnancy is very high.