Time Interval Between Absent and Reversed End-Diastolic Flow in Growth-Restricted Fetuses
The progression from absent end-diastolic flow (AEDV) to reversed end-diastolic flow (REDV) in growth-restricted fetuses is unpredictable and can occur rapidly, necessitating Doppler assessment 2-3 times per week once AEDV is detected due to the potential for deterioration within days. 1
Evidence on Progression Timeline
The available evidence does not establish a specific, predictable time interval between AEDV and REDV. However, the clinical data reveals important patterns:
Rapid deterioration is possible within the first 2 weeks after diagnosis of FGR, with the most critical period for progression occurring early after abnormal Doppler findings emerge 1
Historical observational data from 1991 showed that reverse flow was observed after a mean delay of approximately 6-8 days in high-risk IUGR cases, though this represents older data with different management protocols 2, 3
The progression is sufficiently unpredictable that current guidelines mandate increased surveillance frequency (2-3 times weekly) once AEDV is detected, rather than relying on a specific time interval 1
Clinical Implications for Surveillance
The lack of a predictable timeline is precisely why surveillance intensity must escalate immediately upon detecting AEDV:
Weekly umbilical artery Doppler is recommended for decreased end-diastolic velocity or severe FGR (EFW <3rd percentile) 1
Doppler assessment must increase to 2-3 times per week when AEDV is detected due to the potential for rapid deterioration to REDV 1
Hospital admission should be considered if fetal surveillance more than 3 times per week is deemed necessary 1, 4
Severity Distinction and Management
The distinction between AEDV and REDV carries critical prognostic and management implications:
REDV represents a more severe stage of placental compromise with significantly worse outcomes, including perinatal mortality rates of 46% in historical series compared to 20% with AEDV 1
REDV mandates immediate hospitalization, antenatal corticosteroids, heightened surveillance with cardiotocography at least 1-2 times daily, and consideration of delivery 1, 5
Delivery timing differs substantially: AEDV warrants delivery at 33-34 weeks, while REDV warrants delivery at 30-32 weeks 4, 5, 6
Research Evidence on Progression Patterns
Recent studies provide additional context on deterioration patterns:
In a 2022 study, progression to REDV occurred in 7.9% of cases with intermittent AEDV versus 25.6% with persistent AEDV, suggesting that the pattern of AEDV (intermittent vs persistent) influences progression risk 7
A 2024 study found that with normal Doppler indices, significant deterioration to AEDV/REDV is unlikely until 4 weeks after FGR diagnosis, but once abnormal indices appear, progression can be more rapid 8
Critical Clinical Pitfalls
Do not assume a predictable timeline exists - the progression from AEDV to REDV can occur within days and requires intensive monitoring 1
Distinguish between intermittent and persistent AEDV (<50% vs ≥50% of cardiac cycles), as persistent AEDV carries higher risk of progression to REDV 7
Earlier gestational age at FGR diagnosis and chronic hypertension are risk factors for more rapid Doppler deterioration 8
Once REDV develops, do not delay delivery - this represents extreme placental insufficiency with high perinatal mortality risk 1, 5, 2