Doppler measurement of uterine arteries during pregnancy

Doppler measurement of uterine arteries during pregnancy

The main trunk of the uterine artery and its main branches at the junction of the uterine body and cervix (adjacent to the internal opening of the cervix) can be easily shown by real-time color Doppler ultrasound. The uterine artery Doppler measurement can be performed by transabdominal ultrasound or transvaginal ultrasound at this position. The absolute uterine artery velocity has no clinical significance, and the pulsatility index (PI) of the left and right uterine arteries is usually obtained for analysis.

▲ Uterine artery anatomy diagram: the main trunk of the uterine artery from the internal iliac artery continues into two branches at the lateral edge of the junction between the uterine body and the cervix (the internal opening of the cervix), the upward uterine body artery and the downward cervical artery. The uterine artery Doppler measurement point should be selected in the arterial trunk before the bifurcation (inside the green coil).

▲ Uterine artery spectrum during pregnancy: the above figure shows the normal spectrum in the second trimester, and the high diastolic blood flow velocity spectrum has no notch, representing the low resistance state of uteroplacental circulation; The following graph shows the abnormal spectrum in the early second trimester, the mid-systolic and early diastolic spectral notch, and the low diastolic blood flow velocity, indicating a high uteroplacental circulation resistance state.

Evaluation of uterine artery Doppler in the first trimester

The uterine artery pulsatility index in the first trimester is an indicator for comprehensive assessment of preeclampsia.

Transabdominal ultrasound: the midsagittal plane above the pubic symphysis was obtained, the inner cervical opening was identified, and the probe was tilted to one side until the vascular plexus was displayed. The main uterine artery was identified by color doppler, and the spectral doppler sampling gate was placed in the main uterine artery (1cm below the bifurcation point) for measurement. If the parameters of ultrasound instrument are set properly, if the measured PSV< 60 cm/s, suggesting that the sampling gate was placed in the branch rather than the trunk, necessitating redetermination of the uterine artery trunk measurement.
The contralateral uterine artery was measured in the same procedure steps.

Transvaginal ultrasound technique: pregnant women empty the bladder, take the lithotomy position, and the probe is placed in the lateral fornix, similar to the transabdominal technique, showing the lateral vascular plexus of the inner cervical orifice. The measurement is completed according to the above transabdominal ultrasound steps.

▲ Examples of early pregnancy uterine artery spectrum obtained by transabdominal ultrasound.

Evaluation of uterine artery Doppler in the second and third trimester

Transabdominal ultrasound technique: the probe was placed longitudinally in the lower abdomen, and the probe was tilted to one side. The external iliac artery was found by parasagittal view, and the uterine artery crossing the external iliac artery was identified by color Doppler. The uterine artery extended along one side of the uterus to the fundus of the uterus. The scanning direction of the probe was adjusted to make the direction of the main trunk of the uterine artery as parallel as possible to the acoustic beam, and the spectrum Doppler sampling gate was placed in the trunk 1 cm below the crossing point for measurement. The contralateral uterine artery was measured by the same procedure.
Transvaginal ultrasound technique: pregnant women empty the bladder, take the lithotomy position, and the probe is placed in the lateral fornix, similar to the transabdominal technique, showing the lateral vascular plexus of the inner cervical orifice. The measurement is completed according to the above transabdominal ultrasound steps.

▲ The normal spectrum of uterine artery in the second and third trimester is obtained by abdominal ultrasound example.

▲ Identification method of uterine artery in middle and late pregnancy: yellow arrow indicates the external iliac artery, green arrow indicates the main uterine artery.

Matters needing attention

Uterine artery Doppler is only suitable for pregnant women with normal uterus, not for those with uterine congenital malformation. The measurement point was selected at the main uterine artery (1cm below the bifurcation point). Generally, 3 to 5 cardiac cycle spectra were selected to measure the pulsatility index. The notch in the early diastole of the spectrum was mostly abnormal. The left and right uterine arteries were measured and recorded, and the mean value of the left and right uterine arteries was analyzed.