Risk of gestational trophoblastic neoplasia after hCG normalisation according to hydatidiform mole type.

Objective: The risk of gestational trophoblastic neoplasia (GTN) after a hydatidiform mole (HM) is well known. However, the risk of GTN after normalisation of hCG in HM is poorly reported. The aim of this study was to evaluate the risk of GTN after normalisation of hCG according to HM types.

Methods: This prospective cohort study carried out between 2000 and 2010 used the database of the French Trophoblastic Disease Centre (FTDC). A total of 2008 registered patients with ascertained types of HM were analysed. Cases of GTN occurring after normalisation of hCG were analysed.

Results: A GTN developed in 239 out of 1980 HMs (12.1%) and 6 out of these 239 post-molar GTN (2.5%) were diagnosed after normalisation of hCG. The risk of GTN after normalisation of hCG was 0.34% (6/1747) following a HM, 0% (0/593) after a partial HM (PHM), 0.36% (4/1122) after a complete HM (CHM), and 9.5% (2/21) after a multiple pregnancy with HM.

Conclusions: The risk of post-molar GTN justifies hCG monitoring in all women with HM. However, after normalisation of hCG, monitoring of PHM can be stopped safely while it should be maintained for CHM and more importantly for multiple pregnancies with HM.