Screening for aneuploidy in the first trimester by assessment of blood flow in the ductus venosus.

OBJECTIVE

To assess the role of ductus venosus Doppler assessment in screening for fetal aneuploidy in pregnancies at 11-14 weeks of gestation.

DESIGN

Prospective observational study.

SETTING

A tertiary referral fetal medicine unit.

POPULATION

Two hundred fifty-six consecutive pregnancies between 11 and 14 weeks of gestation referred to our unit.

METHODS

Nuchal translucency was measured and colour Doppler imaging was used to assess normal (forward) or abnormal (absence/reversed) ductus venosus flow during atrial contraction.

MAIN OUTCOME MEASURES

Fetal karyotype, structural abnormalities and pregnancy outcomes.

RESULTS

The nuchal translucency measurement was > or = 95th centile in 90 (35.2%) pregnancies, and 123 (48.0%) had a nuchal translucency-related risk of > or = 1:300. There were 46 chromosomally abnormal pregnancies and six euploid pregnancies with adverse outcome. The prevalence of abnormal ductus venosus Doppler waveforms in normal pregnancies was 4.49% (95% CI 1.76-8.76%). The sensitivities of abnormal nuchal translucency measurement alone, ductus venosus velocimetry alone or nuchal translucency and ductus venosus combined for Down's Syndrome were 80.4%, 58.7% and 93.5%, respectively. The likelihood ratios for aneuploidy with abnormal nuchal translucency measurement alone, ductus venosus velocimetry alone or nuchal translucency and ductus venosus combined were 3.33, 9.83 and 3.48, respectively.

CONCLUSION

There is clear association between abnormal flow in the ductus venosus and fetal aneuploidy. The use of ductus venosus velocimetry in combination with nuchal translucency is better than either test alone, since it increases the sensitivity in the detection of Down's Syndrome to 94% and decreases the likelihood ratio of a negative test to 0.08.