Screening for preeclampsia

In the measurement of the uterine artery pulsatility index (PI) the gestation should be 11⁺⁰-13⁺⁶ weeks and the crown-rump length 45-84 mm.

• A sagittal section of the uterus should be obtained and the cervical canal and internal cervical os identified.
• The transducer should be gently tilted from side to side and 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 care should be taken to ensure that the angle of insonation is less than 30º.
• When three similar consecutive waveforms are obtained the uterine artery PI should be measured and the mean uterine artery PI of the left and right arteries calculated.