Early pregnancy is frequently accompanied by abnormal symptoms such as pelvic pain and metrorrhagia. In these situations, it is quite frequent to be unable to identify the pregnancy and in particular its location, even if the pregnancy test is clearly positive. Many clinical, biological and ultrasound approaches have been proposed to try to predict the location and development of the suspected pregnancy, without the individualization of a truly reliable tool. Currently the HCG dosage at 48 heures-interval remains one of the best tools available, but it is challenged by mathematical models such as the M6 model. The M6 model has shown in our experience a very good predictive value with also an ability to reduce the follow-up of patients with low progressive risk, thus allowing a reduction in costs and anxiety for patients and caregivers.