Absent End-Diastolic Flow

Absent end diastolic flow is the absence of forward blood flow in the umbilical artery during diastole on Doppler. It indicates obliteration of many of the placental small vessels.

It matters because it carries a high risk of fetal hypoxia, stillbirth and perinatal death, and it leads to reversed flow in some pregnancies within days.

Usually accompanies fetal growth restriction and often preeclampsia.

Risk factors: severe preeclampsia, antiphospholipid syndrome, chronic hypertension, kidney disease, smoking.

Progression to reversed end diastolic flow can occur within days.

Women may have reduced fetal movements, hypertension, proteinuria and a small fundal height, or have no symptoms. The finding is made on scan.

• Small abdomen and low liquor.

• Raised blood pressure from coexisting hypertension or preeclampsia.

Differential diagnosis: technical artefact (fetal breathing, probe pressure), constitutionally small fetus, chromosomal abnormality, congenital infection, fetal anomaly.

Complications: stillbirth, fetal acidosis, preterm birth, intrapartum hypoxia, necrotising enterocolitis, neonatal death, cerebral palsy.

The approach is repeat Doppler with staging of fetal condition.

• Umbilical artery Doppler repeated in 24 hours; confirm absence of flow in diastole over several cardiac cycles in a free loop.
• Estimated fetal weight, abdominal circumference, deepest pocket, middle cerebral artery Doppler, ductus venosus Doppler.
• Cardiotocography at diagnosis and daily; computerised short term variation below 3.5 ms where available.
• Maternal: blood pressure, urine protein to creatinine ratio, platelets, liver enzymes, creatinine, antiphospholipid antibodies.

The principle is admission, steroid and magnesium cover and delivery at about 34 weeks, earlier if the fetus deteriorates.

• Supportive: admit after 26 weeks; left lateral rest; Doppler twice weekly; cardiotocography once or twice daily; neonatal unit informed; counselling before 26 weeks.
• Pharmacological: betamethasone 12 mg IM twice, 24 hours apart, from 24 weeks to 34 weeks and 6 days; magnesium sulphate 4 g IV over 20 minutes then 1 g per hour until delivery for 24 hours at most before 32 weeks (stop for absent patellar reflexes, respiratory rate below 12 per minute or urine below 30 mL per hour, with calcium gluconate 1 g IV over 10 minutes for toxicity); labetalol 200 mg oral every 8 to 12 hours (maximum 2.4 g daily) or nifedipine modified release 30 to 60 mg oral once daily (maximum 120 mg) for hypertension; oxytocin 10 IU IM at birth.
• Procedures: caesarean section at 34 weeks, or earlier at once for reversed flow, abnormal ductus venosus, pathological cardiotocography or severe preeclampsia after steroids where time allows; continuous cardiotocography if labour is chosen at 34 weeks with normal ductus venosus and cardiotocography.
• Special groups: severe preeclampsia needs magnesium sulphate 4 g IV then 1 g per hour for 24 hours after birth and labetalol 20 mg IV then 40 mg, 80 mg and 80 mg at 10 minute intervals (maximum 220 mg); newborns have glucose checked at 2 hours, and glucose below 2.6 mmol/L is treated with dextrose 10 percent 2 mL/kg IV over 10 minutes then 80 mL/kg per day.
• Red flags: reversed flow, abnormal ductus venosus, pathological cardiotocography, absent fetal movements, severe hypertension, bleeding.
• Follow-up: Doppler twice weekly; daily cardiotocography; growth every 2 weeks; neonatal follow-up at 2 years.