Accuracy of fetal anatomy survey in the diagnosis of velamentous cord insertion: a case–control study

OBJECTIVE: Our objective was to determine the accuracy of ultrasound at the time of the fetal anatomy survey in the diagnosis of velamentous cord insertion (VCI). STUDY DESIGN: This retrospective case–control study identified placentas with VCI (cases) and randomly selected placentas with normal placental cord insertion (PCI) (controls) as documented by placental pathology for mothers delivered from 2002 through 2015. Archived ultrasound images for PCI at the time of the fetal anatomy survey were reviewed. Data analysis was by calculation of sensitivity, specificity, and accuracy and their 95% CI for the ultrasound diagnosis of VCI. RESULTS: The prevalence of VCI was 1.6% of placentas submitted for pathologic examination. There were 122 cases of VCI and 347 controls with normal PCI. The performance criteria calculated for the diagnosis of VCI at the time of fetal anatomy survey were as follows: sensitivity 33.6%; 95% CI: 25.3, 42.7; specificity 99.7%; 95% CI: 98.4, 99.9 and accuracy 82.5; 95% CI: 80.5, 82.9. CONCLUSION: The identification of a VCI at the time of fetal anatomy survey is highly specific for the presence of a VCI as documented by placental pathology. The sensitivity in this study was less than expected. Sensitivity could be improved by reducing the number of nonvisualized PCIs, creating an awareness of risk factors for VCI, and obtaining more detailed images in the case of an apparent marginal PCI.