Size and Number of Placental Lakes on 20-Week Anatomy Ultrasound and Obstetric Outcomes [A190

Abstract

INTRODUCTION: Placental lakes are vascular spaces within the placenta filled with maternal blood which appear hypoechoic on ultrasound. They are frequently dismissed as a benign finding despite limited data. The objective of this study was to determine whether large lakes or multiple lakes are associated with an increased risk of adverse pregnancy outcomes. METHODS: Retrospective cohort of all pregnant women with placental lakes on 20-week fetal anatomy ultrasound from January 2018 to July 2021 who delivered at one of seven hospitals in a large health system. Exclusion criteria were multiple gestations, placenta previa, and invasive placentation. For each patient, clinical characteristics were obtained and ultrasound images were reviewed to determine whether multiple lakes were present and to measure the lake with the longest dimension. Patients with small placental lakes (<5 cm) were compared to those with large placental lakes (≥5 cm). The outcomes of interest were preterm birth, low birth weight, mode of delivery, and preeclampsia. Institutional review board approval was obtained. RESULTS: A total of 210 patients were included for analysis: 23 (11%) had large placental lakes and 187 (89%) had small placental lakes. The mean largest dimensions were 6.3 cm and 3.0 cm in each group, respectively. Multiple lakes were observed in 163 cases (78%). No demographic differences were noted between groups. There was no difference in gestational age at delivery, preterm birth, cesarean delivery, preeclampsia, or birth weight between groups. CONCLUSION: Placental lakes identified on 20-week fetal anatomy ultrasound, even when larger than 5 cm or multiple, were not associated with adverse pregnancy outcomes.