An ultrasound scan at around 24 weeks of pregnancy has been shown to be useful in identifying pregnant women at increased risk of pre-eclampsia and babies at risk of significant growth problems. Closer monitoring of the pregnancy and specific treatment may improve the outcome of the pregnancy. |
WHO SHOULD HAVE A UTERINE ARTERY SCAN?
The scan is useful for both low risk women having an uncomplicated pregnancy as well as those with risk factors such as hypertension, a previous history of pre-eclampsia or a poorly grown baby due to poor placental function.
UTERINE ARTERY BLOOD FLOW IN NORMAL PREGNANCY
In normal pregnancies there are multiple thin walled widely open 'spiral arteries' carrying maternal blood to the placental bed to supply oxygen and nutrients to the baby. The normal uterine artery blood flow pattern shows high flow throughout the cardiac cycle.
NORMAL UTERINE ARTERY WAVEFORM
Women with normal uterine artery blood flow waveforms have a low risk of developing pre-eclampsia and obstetric complications related to uteroplacental insufficiency.
UTERINE ARTERY BLOOD FLOW IN ABNORMAL PREGNANCY
At 24 weeks about 5% of pregnancies show poor blood flow (high impedance) during the second half of the cardiac cycle and often they have a deep notch in the uterine artery waveform.
ABNORMAL UTERINE ARTERY WAVEFORM WITH NOTCHING
Abnormal uterine artery blood flow waveforms in both high-risk and low-risk pregnancies are associated with increased risk for subsequent development of pre-eclampsia (50%), severe pre-eclampsia (75%) and intrauterine growth retardation (30%).
Abnormal Doppler is also better in predicting clinically significant growth retardation such as those with birthweights less than 3rd centile or pregnancies requiring delivery before 35 weeks because of placental insufficiency rather than mild growth retardation.
In pregnancies with abnormal uterine artery blood flow patterns, closer surveillance and early detection of pre-eclampsia and growth retardation may improve the outcome for both mother and baby.
Treatment of hypertension and early delivery may be necessary for the safety of both mother and baby.
Prophylactic steroids may reduce the risk of breathing problems in the baby if early delivery is planned.
|Colour Doppler image of Uterine Artery as it crosses over the Iliac Artery |
|Normal Uterine Artery Doppler Waveform |
|Abnormal Uterine Artery Doppler Waveform (with notching) |