Placental Cysts and Atypical Sonolucencies at 11-13 Weeks' Gestation: Sonographic Features and Clinical Significance.

Objectives: The aim of this study was to determine the sonographic features, antenatal course, and pregnancy outcome in pregnancies in which a placental cyst (PC) or a placental atypical sonolucency (PAS) was identified at the routine first-trimester scan.

Methods: Pregnancies in which a first-trimester PC/PAS was sonographically detected at 11-13 weeks' gestation were recruited. Relevant information was obtained by reviewing ultrasound reports and medical records.

Results: A PC/PAS was identified in 12 of 8150 first-trimester pregnancies undergoing sonographic screening (prevalence 1/679; 0.15%). Median gestational age at evaluation was 13 weeks + 3 days (range, 11 + 1-13 + 6). Monochorionic twin pregnancy was detected in one case. Median cyst diameter was 11 mm (range, 7-26). The cyst was single in 10 cases (83%) and multiple in the other two (17%). Four (33%) were eccentric and eight (67%) were central in location. Except for three pregnancies complicated with multiple major anomalies, the prognosis was universally good in the remaining cases, with resolution or spontaneous involution in all continuing pregnancies.

Conclusions: A PC/PAS is an uncommon finding during the 11-13 weeks scan. It is often incidental, transient, and according to our experience of no clinical significance in isolated cases. When detected in fetuses with congenital anomalies, the final prognosis depends on the associated fetal malformations.