EP16.40: Massive retroplacental lake in a third trimester pregnancy without any adverse outcomes

Placental lakes are the prevailing placental characteristic observed in grayscale ultrasonography imaging. They are defined as homogeneous anechoic areas, surrounded by placental tissue of normal echogenicity, and often found in the centre of the lobule, in the marginal zone, or under the chorionic plate. The size, shape, and quantity of placental lakes might vary as the pregnancy progresses. The clinical significance and etiology of these conditions remain uncertain. They could potentially be linked to pre-eclampsia and fetal growth restriction (FGR) if they are classified as large (between 2 and 5 cm) or not linked to particular prenatal problems. The patient, primigravid, aged 31, was followed up in our hospital for a pregnancy examination. In routine ultrasound examination, a large placental lake (8x16 cm in diameter) under the basal plate was recognised at gestational week 32. The patient had not been diagnosed with placental lakes before. The patient was followed until the 38th gestational week and admitted to the hospital at 32 weeks gestation for observation. After that, she was re-admitted at 34 weeks gestation due to the beginning of uterine contractions. The patient was hospitalised for 2 days, and tocolytic drugs and steroids were administered. Despite the large retroplacental lake, no complications such as pre-eclampsia or FGR developed. At week 38 of pregnancy, the patient gave birth to a live girl via Caesarean section. Placental pathology revealed perivillous fibrin deposition in line with placental lake formation. Placental abruptions were not present. In conclusion, large placental lakes in atypical locations, such as in the posterior part of the placenta, can be encountered during third trimester sonography, although their clinical significance is debatable. In our case, the massive placental lake resolved without any complications.