Absent umbilical arterial end-diastolic flow

Absent end-diastolic flow (AEDF) in an umbilical artery Doppler assessment is a useful feature which indicates underlying fetal vascular stress if detected in mid or late pregnancy. It is often classified as Class II in severity in abnormal umbilical arterial Dopplers ⁹.

Pathology

The presence of absent end-diastolic flow (AEDF) can be normal in early pregnancy (up to 16 weeks). In mid to late pregnancy it usually occurs as a result of placental insufficiency ^7,8. Flow in the umbilical artery should be in the forward direction in normal circumstances. If placental resistance increases, the diastolic flow may reduce, later becoming absent and finally reverses.

Associations

• intra-uterine growth restriction (IUGR)
• increased risk of neonatal thrombocytopenia ⁶
• increased risk of necrotizing enterocolitis¹

Radiographic features

Doppler ultrasound

The umbilical arterial velocity is seen reducing to zero at end diastole. The impedance is found to be highest at the fetal end of the umbilical cord and therefore the absence of end diastolic flow is seen first in this region.

Treatment and prognosis

The situation is associated with an increased risk of fetal and neonatal mortality, as well as an increased incidence of long-term permanent neurologic damage ⁵.

Approximately 1/3 of cases may improve with bed rest. Often it is recommended that close follow-up or expeditious delivery be pursued ⁷.

See also

• reversal of umbilical artery end-diastolic flow