OBJECTIVE: To test the hypothesis that the application of ductus venosus Doppler velocimetry between 10--14 weeks gestation may serve as a screening tool for the detection of fetuses with Down syndrome and estimate a new criteria of risk. PATIENTS AND METHODS: 491 fetuses were studied consecutively. In 132 cases a cytogenetic study was performed on material obtained from a biopsy of the chorionic villus, and in 359 cases the postnatal phenotype was used as a basis for the result. In addition to the routine ultrasonographic examination, all the fetuses were submitted to measurement of the nuchal translucency thickness. T "student" and ANOVA tests were used for the statistical analysis. The sensitivity, specificity, positive and negative predictive values, true-positive probability and likelihood ratio were calculated. RESULTS: There were 21 cases of Down syndrome. On these 21 fetuses the ductus venosus blood flow during atrial contraction was either absent (n = 3) or reversed (n = 17) - sensitivity = 95.2%. In the chromosomally normal fetuses (n = 470) only 8 had abnormal Doppler findings in the ductus venosus (specificity = 98.2%, positive and negative predictive values = 71.4% and 99.8%, respectively, and positive and negative likelihood ratio = 56 and 0.1, respectively). CONCLUSION: Our preliminary results suggest that the presence of Down syndrome may be strongly suspected when there is reverse or absent flow in the ductus venosus Doppler velocimetry during atrial contraction. We speculate the possibility of a new criteria to calculate the new risk of Down syndrome based on Doppler examination of the ductus venosus. Using the program of the Fetal Medicine Foundation to assess the baseline risk, a multiplying factor of approximately 0.1 (negative predictive value) is applied for normal ductus whereas a multiplying factor of 50 is applied in case of reverse or absent ductus, thus establishing a new adjusted risk factor.
Doppler velocimetry; Ductus venosus; Down syndrome; Prenatal diagnosis
