After evacuation of a hydatidiform mole the risk for choriocarcinoma is considered when:

Following evacuation of the uterus, weekly serum Beta -hCG levels should be monitored until normalized for 3 weeks, followed by monthly testing for 6-12 months depending on assessment of pretreatment risk factors. If the Beta -hCG value plateaus for 3 weeks or rises for 2 weeks, invasive gestational trophoblastic disease, including either invasive mole or choriocarcinoma, should be suspected. Effective contraception during the surveillance phase is impoant in order not to complicate interpretation of the Beta-hCG. Ref: Reynolds R. Loar P.V. (2010), Chapter 39, Gynecology ; G.M. Dohey (Ed), CURRENT Diagnosis & Treatment: Surgery, 13th Edition