First-trimester ductus venosus, nasal bones, and Down syndrome in a high-risk population

OBJECTIVE: Assessing the role of fetal ductus venosus and nasal bones evaluation in first-trimester screening for Down syndrome. METHODS: This was a prospective cohort study in a tertiary referral fetal medicine unit involving 628 consecutive fetuses undergoing chorionic villus sampling. The indication for chorionic villus sampling was an increased risk (more than 1:300) for trisomy 21 based on maternal age and nuchal translucency screening in 313 cases (54.7%), increased maternal age in 195 (34.1%), and other in 64 (11.2%). Immediately before chorionic villus sampling, an ultrasound examination was performed. The pattern of blood flow in the ductus venosus and the presence or absence of the nasal bones was noted. RESULTS: A satisfactory examination of both ductus venosus and nasal bones was possible in 572 fetuses. Of these, 497 (86.9%) had a normal karyotype, and 47 (8.2%) were affected with Down syndrome. The likelihood ratio for trisomy 21 was 7.05 (95% confidence interval 4.27-11.64) in the case of abnormal ductus venosus flow and 6.42 (95% confidence interval 3.86-10.67) in the case of absent nasal bones. CONCLUSION: In addition to increased fetal nuchal translucency, Down syndrome is significantly associated with first-trimester abnormal flow velocity patterns in the ductus venosus and hypoplasia of the nasal bones. (c) 2005 by The American College of Obstetricians and Gynecologists.