Antenatal Detection of Abnormal Placental Cord Insertion across Different Trimesters: A Prospective Cohort Study

Objectives This article prospectively examines the use of ultrasound for antenatal detection of abnormal placental cord insertion (PCI) and compares the antenatal classification with delivered placental classification. Study Design This prospective cohort study examined 277 singleton pregnancies in a tertiary center. Scans were performed between 10 and 14, 18 and 22, and 32 and 34 weeks where PCI site was identified and its shortest distance to margin measured. Standardized images of delivered placentas were taken and digitally measured. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of antenatal classification compared with delivered placental classification were calculated. Results Abnormal PCI (distance < 2 cm from margin) was confirmed in 30/277 (11%) placentas at delivery. Note that 102/277 (37%) of PCI sites were classified as abnormal in the first trimester (T1), 43/277 (16%) in the second trimester (T2), and 28/277 (10%) in the third trimester (T3). Sensitivity (73%) and specificity (91%) were highest at T2. The PPVs were low (22% in T1, 51% in T2, and 64% in T3) and the NPVs were high (96% in T1 and 97% in both T2 and T3) for all scans. Conclusion Abnormal PCI can be detected antenatally with optimal agreement with postnatal classification in T2. However, the incidence is overestimated at early scans with low PPVs.