What are the management measures if the uterine artery Pulsatility Index (PI) is above the 95th centile at 20 weeks of pregnancy?

Management of Uterine Artery PI Above 95th Centile at 20 Weeks of Pregnancy

For pregnancies with uterine artery Pulsatility Index (PI) above the 95th centile at 20 weeks, increased surveillance is necessary as this finding indicates higher risk for developing placental insufficiency, preeclampsia, and fetal growth restriction (FGR). 1, 2

Risk Assessment and Initial Management

• Abnormal uterine artery Doppler at 20 weeks (PI >95th centile) is associated with increased risk of preeclampsia, FGR, and adverse perinatal outcomes 3, 2
• Begin low-dose aspirin (100-150 mg) in the evening if not already started, although optimal benefit occurs when initiated before 16 weeks 1
• Perform a detailed obstetrical ultrasound examination to rule out fetal anomalies, especially if there are additional concerning findings 1

Surveillance Protocol

20-32 Weeks (Early Surveillance)

• Schedule growth ultrasounds every 2 weeks to monitor for development of FGR 1
• Perform umbilical artery Doppler assessment every 2 weeks 1
• If normal growth and normal umbilical artery Doppler are maintained, continue this schedule 1

If FGR Develops (EFW or AC <10th percentile)

• Increase umbilical artery Doppler frequency to weekly 1
• Begin weekly cardiotocography (CTG) testing after viability 4, 1
• Consider middle cerebral artery (MCA) Doppler after 32 weeks to assess for brain-sparing effect 1

If Umbilical Artery Doppler Becomes Abnormal (PI >95th centile)

• Increase surveillance to weekly or more frequent assessments 1
• Monitor amniotic fluid volume weekly 1
• Consider referral to maternal-fetal medicine specialist 1

If Absent End-Diastolic Flow Develops

• Hospitalize if before 34 weeks 1
• Administer corticosteroids for fetal lung maturity 1
• Implement daily cardiotocography monitoring 1
• Perform twice-weekly umbilical artery Doppler and amniotic fluid assessment 1
• Consider delivery by 34 weeks gestation 1

If Reversed End-Diastolic Flow Develops

• Immediate hospitalization if before 30 weeks 1
• Administer corticosteroids for fetal lung maturity 1
• Implement daily cardiotocography monitoring 1
• Perform umbilical artery Doppler three times weekly 1
• Consider delivery by 30-32 weeks gestation 1
• Administer magnesium sulfate for fetal neuroprotection if delivery is planned before 32 weeks 1

Timing of Delivery Based on Findings

• With normal umbilical artery Doppler but FGR present: Consider delivery at 37-38 weeks 1
• With abnormal umbilical artery Doppler (increased PI): Deliver by 37 weeks 1
• With absent end-diastolic flow: Deliver by 34 weeks 1
• With reversed end-diastolic flow: Deliver by 30-32 weeks 1
• Earlier delivery may be indicated with deteriorating fetal condition or poor interval growth 1

Mode of Delivery Considerations

• With normal end-diastolic flow: Induction of labor with continuous fetal monitoring is appropriate 1
• With absent or reversed end-diastolic flow: Cesarean delivery is likely recommended 1
• Very preterm gestations with FGR may benefit from cesarean delivery 1

Pitfalls and Caveats

• Uterine artery Doppler alone has modest predictive value (sensitivity 27-35% for preeclampsia) and should not be used in isolation for clinical decision-making 3, 5
• The sensitivity of uterine artery Doppler is higher for early-onset severe complications than for late-onset mild disease 5, 6
• Multiple vessel Doppler assessment provides better risk stratification than single vessel assessment 1
• Avoid multiple courses of corticosteroids as they are not recommended 1
• Consider maternal comorbidities, especially hypertensive disorders, which significantly increase the risk of adverse outcomes 1