Summary

The International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) guidance document proposes evidence-based recommendations that deal specifically with the clinical and technical aspects of ultrasound screening, a non-invasive method to detect poor placental perfusion due to increased uterine PI, associated with pre-eclampsia (PE).

Pre-eclampsia (PE) and its complications are a major contributor to maternal and perinatal morbidity and mortality worldwide with an approximate global incidence of 3%. Given that timely and effective care can improve the outcome of PE, the development of effective prediction and prevention strategies has been a major objective of prenatal care and of research.

The International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) has released evidence-based practice guidelines regarding the role of ultrasound in screening and follow-up of pre-eclampsia (PE). The guidance document has been published in the journal Ultrasound in Obstetrics and Gynecology.

The contributing authors of the guideline write, “For the purpose of this guideline, in the context of PE, ‘screening’ is the preferred term when identification of cases at risk may lead to prevention of its development, whereas ‘prediction’ is the preferred term when there is no evidence that identification of women at risk will eventually improve their outcome.”

Topics covered in the guidelines

• Screening for pre-eclampsia using ultrasound
  • Which Doppler index to use
  • First, second and third trimester
  • Longitudinal changes in Doppler indices
  • Placental volume
• Combined screening strategies
• Assessment of maternal hemodynamics
• Management after screening
• Multiple pregnancy
• Use of ultrasound in patients with established pre-eclampsia

Longitudinal changes in Doppler indices

Preventive strategies (e.g. low-dose aspirin) for reducing the risk of PE should be commenced as soon as possible in the first trimester for high-risk women, without waiting to assess the evolution of Doppler in the second trimester.

Placental Volume

Given the requirement of special equipment, time consumption and limited reproducibility, placental volume and vascularisation indices are not recommended for screening purposes.

Combined screening strategies

• A combination of maternal factors, maternal arterial blood pressure, uterine artery Doppler and PlGF (Placental growth factor) level at 11-13 weeks appears to be the most efficient screening model for identification of women at risk of PE
• 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
• The transabdominal approach is preferred for calculating 1st-trimester individual patient risk

Assessment of maternal haemodynamics

Routine implementation in clinical practice as a stand-alone test is not recommended for the lack of enough data in its support.

Management after screening

Low-dose aspirin can decrease significantly the risk for development of early PE, when commenced at the time of 1st-trimester screening

Multiple pregnancies

1. Due to increased placental mass in twin pregnancy, resulting in lower mean resistance in the uterine arteries, twin-specific reference ranges should be used for Doppler examination, if available
2. The combined screening (maternal factors, uterine artery PI, mean blood pressure, PlGF) algorithm for singletons can also be used in twin pregnancy

• It can identify more than 95% of women with twin pregnancy who will develop PE
• However, the examiner should be aware that this is achieved at the cost of a 75% screen-positive rate