Prenatal color Doppler sonographic evaluation of nuchal encirclement by the umbilical cord.

PURPOSE

The aim of this study was to assess whether Doppler flow velocimetry of the fetal middle cerebral and umbilical arteries is affected by nuchal encirclement by the umbilical cord (nuchal cord) in the prenatal period.

PATIENTS AND METHODS

The position of the fetal umbilical cord was assessed on color Doppler sonography in pregnant women who were referred to our radiology department between September 14, 1998, and January 14, 2000. Pulsatility and resistance indices and the ratio of peak systolic blood flow velocity to diastolic velocity of the umbilical arteries and middle cerebral arteries of all fetuses were prospectively obtained with Doppler flow velocimetry. The fetuses were categorized into 2 groups: group 1 consisted of fetuses without sonographic evidence of nuchal cord and group 2 of fetuses with sonographic evidence of nuchal cord. The results were statistically analyzed with independent-groups t test. A p value of less than 0.05 was considered significant.

RESULTS

During the study period, 230 pregnant women underwent sonographic examination of the fetus, and 68 fetuses were delivered. The sonographic examinations were performed at 24-41 weeks' menstrual age. Of the 46 fetuses in group 1, 1 fetus had nuchal cord at delivery; of the 22 fetuses in group 2, 4 did not have nuchal cord at delivery. The sensitivity of color Doppler sonography in detecting nuchal cord was 95% (18 of 19 fetuses), the specificity was 92% (45 of 49), the negative predictive value was 98% (45 of 46), and the positive predictive value was 82% (18 of 22). No statistically significant differences in middle cerebral artery or umbilical artery Doppler flow velocimetry values were detected between the 2 groups.

CONCLUSIONS

Color Doppler sonography is a sensitive and specific method of diagnosing nuchal cord, but fetal middle cerebral artery and umbilical artery Doppler flow velocimetry values are not affected by the presence of nuchal cord in the prenatal period.