Sonographic appearance of early complete molar pregnancies

Since our anecdotal experience indicates that the classically described "snowstorm" appearance on ultrasonography of early molar pregnancies is often not present and that theca-lutein cysts are also rare, we examined the ultrasonographic appearance of early complete molar pregnancies. We reviewed the ultrasonographic reports and clinical data of 21 cases of histologically diagnosed complete molar pregnancies with a mean gestational age at sonography of 10.5 weeks (range, 4 to 18 weeks). The diagnosis of molar pregnancy was made on ultrasonography in 12 (57%) cases, was second in the differential diagnosis of one (4.8%) case, and was not considered in eight (38%) cases. No theca-lutein cysts were identified. Five of five (100%) molar pregnancies of 13 weeks or over were diagnosed prospectively, while only eight of 16 (50%) earlier pregnancies were correctly diagnosed prospectively. In a retrospective review of the available images of 16 patients, only nine of 16 (56%) images demonstrated the classic appearance, and no theca-lutein cysts were seen. We conclude that the classic appearance of complete moles on ultrasonography is seen in less than two thirds of cases and even less commonly in the first trimester. The prevalence of theca-lutein cysts is very low.