11-13 week scan
Uterine artery PI
FMF Certificate of competence in measurement of uterine artery PI
The Fetal Medicine Foundation has now established software for the calculation of risk for preeclampsia. The software is provided free of charge to those who comply with the FMF regulation of NT screening and have demonstrated competence in the Doppler assessment of the uterine arteries at the 11-13 weeks scan.
Preeclampsia, which affects about 2% of pregnancies, is a major cause of perinatal and maternal morbidity and mortality. Routine antenatal care has evolved with the aim of identifying women at high-risk for subsequent development of preeclampsia. The likelihood of developing preeclampsia is increased by a number of factors in the maternal history, including Afro-Caribbean race, nulliparity, high body mass index and personal or family history of preeclampsia. However, screening by maternal history may detect only about 30% of those that will develop preeclampsia for a false positive rate of 5%.
A more effective method of screening for preeclampsia is provided by measurement of the uterine artery pulsatility index (PI) at 11-13 weeks' gestation in combination with maternal history, blood pressure and serum PAPP-A and placental growth factor (PLGF). For a false-positive rate of 5% it has been estimated that the new combined method of screening can predict 90% of preeclampsia requiring delivery before 34 weeks and 45% of late preeclampsia. There is extensive evidence that it is early rather than late preeclampsia which is associated with an increased risk of perinatal mortality and morbidity and both short-term and long-term maternal complications.
Identification of women at high-risk for preeclampsia during the first trimester could potentially improve pregnancy outcome because intensive maternal and fetal monitoring in such patients would lead to an earlier diagnosis of the clinical signs of the disease and the associated fetal growth restriction and avoid the development of serious complications through such interventions as the administration of antihypertensive medication and early delivery.
It is imperative that, as for the NT scan, sonographers undertaking risk assessment of preeclampsia by examination of the uterine arteries must receive appropriate training and certification of their competence.
Requirements for Certification in measurement of uterine artery PI
The requirements for certification are:
1. FMF certification in the measurement of nuchal translucency.
2. Attendance of the internet based course on the 11-13 weeks scan.
3. Submission of a logbook of 3 images demonstrating color flow mapping and waveforms of the uterine artery at 11-13 weeks.
Protocol for first-trimester measurement of the uterine artery PI
- The gestational age must be between 11 weeks and 13 weeks and six days.
- Sagittal section of the uterus must be obtained and the cervical canal and internal cervical os identified. Subsequently, the transducer must be gently tilted from side to side and then colour flow mapping should be used to identify each uterine artery along the side of the cervix and uterus at the level of the internal os.
- Pulsed wave Doppler should be used with the sampling gate set at 2 mm to cover the whole vessel and ensuring that the angle of insonation is less than 30º. When three similar consecutive waveforms are obtained the PI must be measured and the mean PI of the left and right arteries be calculated.
Submission of logbook
Please login to upload your images:
Alternatively, send your completed logbook to:
The 11-13 weeks scan: Uterine artery PI
The Fetal Medicine Foundation
137 Harley Street
London, W1G 6BG
Holders of the FMF Certificate in measurement of uterine artery PI
To view the list of sonographers who have obtained the Certificate of competence in measuring uterine artery PI for early preeclampsia screening please click here.
Color Doppler of uterine arteries
Uterine artery waveform