Placental surface cysts detected on sonography: histologic and clinical correlation.

Objective: To evaluate the clinical outcome and histologic findings of pregnancies in which placental surface cysts were detected on prenatal sonography.

Methods: A computerized search of our obstetric sonographic database from 1988 through 2000 identified 34 cases. Results of pathologic examinations, when performed, were obtained. Sonographic features were correlated with histologic findings and clinical parameters.

Results: On review of available microscopic slides, in all cases in which the cyst was seen at pathologic examination, there was subchorionic fibrin with central cyst formation. All pregnancies resulted in live births, although intrauterine growth restriction occurred in 4 (12%) of 34. Three (11%) of 28 cases with placental pathologic findings had maternal floor infarction. Only 2 significant associations between sonographic features and postnatal findings were found. In all cases of intrauterine growth restriction, average cyst size was larger than 4.5 cm. Of 12 cysts larger than 4.5 cm, 4 (33%) had intrauterine growth restriction. Of 22 cysts smaller than 4.5 cm, there were no instances of intrauterine growth restriction (P = .01). Of 32 cases with 3 or fewer cysts, only 2 had intrauterine growth restriction, whereas in 2 cases with more than 3 cysts, both had intrauterine growth restriction (P = .01).

Conclusions: Most placental surface cysts are associated with a normal pregnancy outcome. Most such cysts are related to cystic change in an area of subchorionic fibrin. Cysts larger than 4.5 cm or more than 3 in number are more frequently associated with intrauterine growth restriction.