SONOGRAPHIC EVALUATION OF THE PLACENTAL CORD INSERTION SITE

OBJECTIVE. Velamentous and marginal umbilical cords are uncommon abnor malities of placental cord insertion that can entail significant fetal risk. We undertook this investigation to assess the ability of prenat al sonography to reveal abnormal insertions of the umbilical cord into the placenta. SUBJECTS AND METHODS. Forty-six patients had both prena tal sonographic evaluation of the placental cord insertion site and po stnatal pathologic examination. Distance from the insertion site to th e nearest placental edge was categorized by sonography and pathology a s normal if greater than 1 cm and abnormal if less than or equal to 1 cm. Sonographic and pathologic findings were compared. RESULTS. Thirty -eight singleton and eight twin pregnancies, for a total of 54 cord in sertions, were studied. Of the 43 sonographically normal insertions, 3 8 had normal pathologic findings, and the remaining five insertions ha d abnormal pathologic findings (all marginal cord insertions). All 11 insertions that showed abnormality on sonography were abnormal on path ologic examination (seven marginal and four velamentous insertions). S onography was able to reveal a difference between the two types of abn ormal insertions in only a single patient, ire whom the cord insertion changed from marginal to velamentous during a 7-week interval. Sonogr aphy had an overall sensitivity of 69% (11/16), a specificity of 100% (38/38), and an accuracy of 91% (49/54) fbr revealing abnormal placent al cord insertion sites. CONCLUSION. Targeted sonographic examination of the placental site of umbilical cord insertion will reveal abnormal placental cord insertions, although distinguishing the specific type of abnormal insertion may require the use of color Doppler imaging.