Prenatal Ultrasound – Placental Lake in High-Risk Pregnancy

We want to present a case of an unusual sonolucent ultrasound (US) finding in the placenta of a 42-year old woman at 35 + 4 / 7 weeks’ gestation (G3, P2, Ab 0). The mother’s medical history was significant for a cleft palate without surgical repair, seronegative spondyloarthropathy, Raynaud’s syndrome and Hashimoto’s thyroiditis, hypothyreosis treated with hormonal supplementation and two prior uncomplicated pregnancies. Mild hypertension was detected in the first trimester and at 17 weeks’ gestation, Methyldopa (3 × 250 mg / day) was prescribed. Early amniocentesis showed a normal male karyotype (46XY). At 33 weeks’ gestation she was admitted because of moderate hypertension and contractions recorded on cardiotocography. Dexamethasone (4 × 6 mg) was given for fetal lung maturation. During hospital stay a routine US exam revealed an unusual sonolucent area (36 × 23 mm in size) in the placenta. Other laboratory findings and clinical examinations were in the reference range for gestational age. At 34 + 3 / 7 weeks’ gestation she was discharged with antihypertensive therapy, Methyldopa 4 × 250 mg / day and normal blood pressure. At 35 + 3 / 7 weeks’ gestation she was admitted to delivery room with regular contractions and preterm premature rupture of membranes. Following admission, US examination was repeated. The diagnosis of an unusual placental lake (33 × 27 mm in size) with hyperechogenic spiral echo and fluctuation of anehogenic liquid inside was confirmed (‣ Fig. [ 1 a, b ]). Dinoproston cervical gel was administered for cervical maturation. The delivery was unremarkable. At 35 + 3 / 7 weeks’ gestation preterm male baby, birth weight and length 2870 g and 49 cm (75th centile) respectively was born. Apgar score was 9 / 10 at 1 and 5 minutes after birth. Immediately after birth the child was admitted to the neonatal intensive care unit. The third and fourth stages of labor were unremarkable. According to pathological report placenta measured 20 : 20 : 2.5 cm, weighted 560 grams. A true knot was found in 52-cm-long umbilical cord with central placental insertion. On the cut surface multiple placental lakes were found up to 3 cm in diameter (10 % of placental volume). Morphologic examination of placenta revealed terminal villi showing syncytial knotting with a focal fibromuscular sclerosis, stromal fibrosis and hypercapillarization (30 %; 20 %; 10 %, respectively). Chronic villitis was found in the placental lake wall (‣ Fig. [ 2 a, b ]).

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