In a case of vesicular mole, all of following are high risk factors for the development of choriocarcinoma, EXCEPT:

High risk factors which indicates the development of choriocarcinoma at the time of diagnosis of a hydatidiform mole are: Maternal age more than 40 years Excessive uterine enlargement Serum hCG levels more than 100,000mIU/ml Theca lutein cysts greater than 6 cm in diameter Toxemia, hypehyroidism and coagulopathy Trophoblastic embolization Previously treated choriocarcinoma Ref: A Practical Approach to Gynecologic Oncology By Basu page 142.