Absence of an anatomical origin for altered ductus venosus flow velocity waveforms in first-trimester human fetuses with increased nuchal translucency

Objective: To perform a morphological evaluation of the ductus venosus, heart and jugular lymphatic sac (JLS) in first-trimester human fetuses with normal and abnormal ductus venosus flow velocity waveforms (DV-FVWs) and normal and increased nuchal translucency (NT). Method: Postmortem examination was performed on fetuses with increased NT or structural malformations with previous NT and DV-FVW measurements. Ductus venosus morphology was examined using markers for endothelium, smooth muscle actin (SMA), nerves and elastic fibers. Fetal hearts were studied by microscopy. The nuchal region was analyzed using markers for lymphatic vessels, endothelium, SMA and nerves. Results: Two trisomy 21 and two trisomy 18 fetuses with increased NT and abnormal DV-FVWs were analyzed. As a control, one euploid anencephalic fetus with normal NT, cardiac anatomy and DV-FVWs was examined. Similar endothelial and SMA expression was observed in the ductus venosus in all fetuses. Nerve and elastic fiber expression were not detected. Three trisomic fetuses showed cardiac defects, one trisomic fetus demonstrated normal cardiac anatomy. The JLS was abnormally enlarged or contained red blood cells in all trisomic fetuses. The control fetus showed a normal JLS. Conclusion: Abnormal DV-FVWs are not justified by alterations in ductus venosus morphology. DV-FVWs most probably reflect intracardiac pressure. What's Already Known About This Topic? Ultrasound examination of ductus venosus flow velocity waveforms is used to indirectly assess fetal cardiac function and the fetal hemodynamic condition. Abnormal first-trimester ductus venosus flow velocity waveforms are related to chromosomal abnormalities, cardiac defects and increased nuchal translucency. Abnormal formation of the jugular lymphatic sacs is involved in the development of increased nuchal translucency. What Does This Study Add? Abnormal ductus venosus flow velocity waveforms are not caused by local alterations in ductus venosus morphology but reflect a changed hemodynamic status. The morphology of the ductus venosus is not related to abnormal ductus venosus flow velocity waveforms, chromosomal abnormalities, cardiac anatomy and increased nuchal translucency. Increased nuchal translucency in first-trimester human fetuses coincides with abnormal jugular lymphatic sac development.