1053: Accuracy of mid-trimester ultrasound (u/s) in the prediction of placental cord insertion

Abstract

Abnormalities of placental cord insertion (PCI) at term has been associated with adverse obstetrical outcomes. If abnormal PCI could be reliably identified antenatally, enhanced fetal and obstetrical surveillance could potentially mitigate these associated risks. Although high resolution ultrasound (U/S) has proven useful in identifying PCI abnormalities in select obstetrical populations, the extent to which routine mid-trimester U/S screening can identify and accurately predict abnormalities of PCI at delivery is unknown. This study evaluated the feasibility of mid-trimester U/S PCI localization to correctly predict PCI at delivery. Prospective observational trial including patients with singleton gestation between 18-22 weeks presenting for fetal anatomical screening U/S at a single institution between 1/1/2013- 12/31/2013. PCI was assessed using gray scale and color doppler and categorized as central/eccentric, marginal (<2 cm was placental edge) or velamentous. The study group was comprised of those patients who delivered at the study site, in whom placenta was examined and PCI similarly categorized following delivery. The accuracy of mid-trimester U/S to predict PCI at delivery was determined by comparing antenatal prediction with actual PCI after delivery. The screening efficacy of mid-trimester U/S to predict abnormal PCI (marginal or velamentous) at term was determined. PCI was localized and documented in 919/942 (97.5%) at time of the mid-trimester screening ultrasound, PCI(U).The study group included 596 (64.9%) patients who delivered at the study site, in whom PCI was documented after delivery, PCI(D). Abnormal PCI was identified in 23/596 (3.9%) of placentas after delivery- 5 (0.8%) velamentous and 18 (3.0%) marginal insertions. The sensitivity, specificity, negative predictive value, positive predictive value of mid-trimester U/S in predicting abnormal PCI at delivery was 21.7%, 96.0%, 96.8%, and 17.9%, respectively. Although readily imaged at time of mid-trimester U/S, the ability to accurately predict abnormal PCI at delivery is poor. Any proposed antenatal management strategy for PCI abnormalities diagnosed by U/S requires consideration of the prenatal diagnostic limitations.