We undertook a study to determine whether partial hydatidiform mole could be distinguished from other cases of first-trimester missed abortion using ultrasound. Scans from 22 cases of pathologically proved partial hydatidiform mole and 33 cases of first-trimester missed abortion were independently reviewed by three radiologists, each unaware of the final pathologic diagnosis. Using a standard data form, each radiologist recorded the dimensions, shape, and contents of the gestational sac, the sonographic appearance of the decidual reaction/placenta and myometrium, and the presence or absence of adnexal cysts. The following two criteria were found to be significantly associated (P<.05) with the diagnosis of partial mole: 1) ratio of transverse to anteroposterior dimension of the gestational sac greater than 1.5, and 2) cystic changes, irregularity, or increased echogenicity in the decidual reaction/placenta or myometrium. There was high interobserver correlation for both criteria, as measured by the K statistic. In 50% of the cases, either both or neither of these criteria were met. When both criteria were met, the frequency of partial mole was 87%; when neither criterion was met, the frequency of missed abortion was 90%. These results indicate that ultrasound can be of value in predicting a high likelihood of partial mole prior to curettage.
(C) 1989 The American College of Obstetricians and Gynecologists