Subchorionic Placental Cyst in a Woman with Fetal Growth Restriction: A Case Report and Review of the Literature.

Subchorionic placental cysts are rare, and their prevalence, etiology, and impact on pregnancy remain unclear. A 40-year-old woman presented at 283/7 weeks of gestation with asymmetric fetal growth restriction. Ultrasonography at 353/7 weeks of gestation revealed a newly detected cystic mass measuring 4 cm in diameter protruding from the fetal surface of the placenta. On pathological examination after delivery, multiple placental infarctions and multifocal perivillous fibrin deposits were diffusely observed throughout the placenta. Through a review of 16 cases of subchorionic placental cysts, including the present case, we found that the majority of cases exhibited abnormal placental pathology suggestive of hypoxia and were associated with unfavorable pregnancy outcomes, such as fetal growth restriction, preterm birth, and an increased risk of cesarean delivery. We suggest that they are associated with unfavorable pregnancy outcomes and may serve as a clinical marker of placental hypoxia.