Updated diagnostic criteria for partial and complete hydatidiform moles in early pregnancy.

Hydatidiform moles are genetically abnormal conceptions which are associated with an increased risk of development of persistent trophoblastic disease and choriocarcinoma. With the introduction of ultrasound examination as part of the routine clinical management of early pregnancy complications, the majority of molar pregnancies are now evaluated in the first trimester before the classical clinical or pathological features have developed. Diagnosis of both complete and partial hydatidiform mole at this early stage of pregnancy requires the use of appropriate, updated histopathological features which are different from those described in later pregnancy.