Ultrasonography of partial hydatidiform mole.

Partial hydatidiform mole differs from complete mole by its focal distribution, its slower transformation, the presence of an embryo or fetus, and the triploid karyotype. Nineteen pathologically proved cases are presented. Partial mole can be diagnosed by a combination of the following sonographic findings: (a) greatly enlarged placenta relative to the size of the uterine cavity, (b) cystic spaces within the placenta ("molar placenta"), which may not always be present, (c) an amniotic cavity (gestational sac), either empty or containing amorphous fetal echoes, and (d) a well-formed but growth-retarded fetus, either dead or alive.