Ductus venosus in the first trimester: contribution to screening of chromosomal, cardiac defects and monochorionic twin complications.

In the first trimester the ductus venosus can be easily identified with color Doppler and a ductus venosus waveform can be obtained by pulsed Doppler. At 11-13 weeks the prevalence of abnormal a-wave in the ductus venosus is inversely related to fetal crown-rump length and maternal serum pregnancy-associated plasma protein-A (PAPP-A), increases with fetal nuchal translucency (NT) thickness and is more common in women of Black racial origin and in fetuses with abnormal karyotype or cardiac defects. Ductus venosus flow provides an independent contribution in the prediction of chromosomal abnormalities when combined with NT and the maternal serum markers of PAPP-A and free beta-hCG, increasing the detection rate to 96% at a false-positive rate of 2.6%. Abnormal ductus venosus flow increases the risk of cardiac defects in fetuses with NT above the 95th centile, and it may increase the risk in fetuses with normal NT. In twin pregnancies, abnormal ductus venosus flow is associated with chromosomal abnormalities and cardiac defects. In monochorionic twins, abnormal flow in the ductus venosus in at least 1 of the fetuses increases the risk of developing twin-to-twin transfusion syndrome.