Reversed end-diastolic umbilical artery velocity in two cases of trisomy 18 at 10 weeks' gestation.

Doppler velocimetry of the umbilical artery was carried out during routine ultrasound examinations performed immediately before either chorionic villus sampling (n = 383) or genetic amniocentesis (n = 649) in 1032 women referred for prenatal diagnosis at our institution, between 10 and 18 weeks of gestation. Reversed end-diastolic flow was detected in only two cases (0.19%), both of which were affected by trisomy 18. The diagnosis was made at 10 weeks' gestation and, to our knowledge, these are the earliest records of this pathological Doppler pattern. Although a possible relationship with early abnormal placentation remains to be established, the finding of reversed end-diastolic velocities in the umbilical artery in the first trimester of pregnancy may be an early sign of karyotype abnormality.