ISUOG Recommendations for Preeclampsia Prevention: Combined Screening and the Role of Ultrasound image

ISUOG Recommendations for Preeclampsia Prevention: Combined Screening and the Role of Ultrasound


The ISUOG Clinical Standards Committee, based on the latest evidence, has released practice guidelines that provide recommendations regarding the role of ultrasound in screening for and follow-up of preeclampsia. Preventative strategies (such as low-dose aspirin) for preeclampsia are effective if started in the first trimester and should begin as soon as high-risk status is identified.  

Given the superiority of combined screening, the use of Doppler cut-offs as a standalone screening modality should be avoided if combined screening is available (GRADE OF RECOMMENDATION: B)

Note: Screening refers to identification of at risk cases that may lead to prevention | Prediction refers to ability to identify at risk cases, but no evidence available regarding improved outcomes  

Combined Screening
Ultrasound Only
Multifetal Pregnancies


Combined Screening (10-13 weeks) – Preferred where available   

  • ASPRE trial results with a 10% FPR (see ASPRE summary in ‘Related ObG Topics’ below) 
    • 100% detection rate for preeclampsia <32 weeks 
    • 75% detection rate for preeclampsia <37 weeks 
    • 43% detection rate for preeclampsia ≥37 weeks 

Combined screening approach is preferred over ultrasound alone and includes the following (see summary of ASPRE algorithm details in ‘Related ObG Topics’ below)   

  • Maternal factors 
    • History | Demographics | CVD and metabolic profile  
  • Maternal arterial BP
  • Placental growth factor (PlGF) 
  • Pulsatility index (PI) should be used to assess uterine artery resistance  
    • Transabdominal approach preferred as used for most studies   
    • Transabdominal: Use color flow mapping on a mid-sagittal view of the uterus at the level of the cervical internal os (transabdominal approach)  
    • Transvaginal: Also obtain mid-sagittal view of the uterus, with lateral movement until paracervical vascular plexus is seen and uterine artery is also at the level of the internal cervical os  
    • Identify an ascending or descending branch of the uterine arteries 
      • Narrow Doppler sampling gate (2 mm) 
      • Insonation angle <30 degrees 
      • Peak systolic velocity of a uterine artery should be greater than 60 cm/s 
      • PI measurement obtained when 3 identical waveforms are captured  
    • 95th percentile uterine artery mean PI (11-13 weeks) 
      • Transabdominal: 2.35  
      • Transvaginal 3.10 for CRL up to 65 mm 
    • Uterine artery PI may be affected by  
      • Ethnicity: African origin has higher PI 
      • Obesity: Decreasing PI with increasing BMI 
      • History of preeclampsia: Increased PI 

Note: Placental volume and vascularization indices are not recommended | Combined screening in the second trimester compares favorably to first trimester, but aspirin intervention is ineffective if initiated >20 weeks

Ultrasound Screening Only  

First Trimester Ultrasound Screening (10-13 weeks) 

  • Due to maternal effects and lesser performance, uterine artery PI is not preferred as a stand-alone test based on cut-offs, but should preferably be incorporated into a combined, multifactorial screening model (see above) 
  • Uterine artery PI >90th percentile in the first trimester detects  
    • 47.8% of women who will develop early PE (7.9% FPR) 
    • 26.4% of women who will develop any PE (6.6% FPR) 
  • PI is superior to resistance index (RI) or uterine artery notching as a preeclampsia predictive tool 
    • PI is more stable than RI, and may still be used in cases of absent or reversed diastolic values 
    • Uterine artery notching is a subjective measure with low specificity
      • Associated with 22-fold increased risk for preeclampsia and 9-fold increased risk for an SGA neonate 
      • However, may be observed in up to 50% of patients at 11-13th weeks 

Second Trimester Ultrasound Screening  

  • Uterine artery PI may be performed at time of the second trimester scan (10% FPR) 
    • 85% detection of early-onset preeclampsia  
    • 48% detection of late-onset preeclampsia  
  • 95th percentile uterine artery mean PI (23 weeks) 
    • Transabdominal: 1.44  
    • Transvaginal: 1.58  

Third Trimester Ultrasound Screening  

  • Use of PI during this period is not recommended due to insufficient outcomes data

Multifetal Pregnancies 

  • Use twin-specific reference ranges  
    • Increased placental mass and lower mean uterine artery resistance seen in multiple gestation 
    • Combined screening approach 
      • >95% detection 
      • 75% screen positive rate

Learn More – Primary Sources:

ISUOG Practice Guidelines: role of ultrasound in screening for and follow up of pre-eclampsia