Doppler in Obstetrics and Gynecology

Doppler velocimetry is a noninvasive way of assessing blood flow by characteristic downstream impedance.

Principle :

When sound waves strike a moving target, the frequency of sound waves reflected back is shifted proportionate to the velocity and direction of the moving target. As the magnitude and direction of the frequency shift depend on the relative motion of the moving target, the velocity and direction of the target can be determined.

In obstetrics :

Doppler is used to determine the volume and rate of blood flow through the maternal and fetal vessels.

Here the sound source is the ultrasound transducer, the moving target is the red blood cells flowing through the circulation. The reflected sound waves are observed by the ultrasound transducer.

Uses :

Recommended as possible adjunct to other fetal evaluation techniques.

Antepartum fetal heart rate testing :

 

In detecting the fetal heart rate patterns, accelerations or decelerations in fetal heart rate, used in nonstress test, contraction stress test, biophysical profile etc.

Doppler index:

 

 

The umbilical artery systolic/diastolic (S/D) ratio is most commonly used Doppler index.

S/D ratio = maximum(peak) systolic flow/ end diastolic flow

By this the ratio evaluates the down stream impedance of the flow. 

The resistance to umbilical artery blood flow during diastole will be initially high then decreases as the gestational age progresses.

Normal flow :

S/D ratio 4.0 at 20 weeks to 2.0 at 40 weeks.

Abnormal flow:

If elevated 95^th percentile of the gestational age

If diastolic blood flow is either absent or reversed.

It indicates extreme downstream resistance, placental dysfunction and fetal compromise with chances of growth restriction.

In estimating fetal maturity:

 

Fetal maturity can be estimated by adding 30 weeks to the date of fetal heart detection by Doppler ultrasound.

In conditions like postterm pregnancy, diabetes, systemic lupus erythematosus, antipospholipid antibody syndrome or in general obstetric population Doppler is ‘not of’ much use.

In Gynecology :

In Gynecology also Doppler is used in different conditions to evaluate the blood flow pattern of different organs and the possible causes for them like,

 

1. In ovarian and endometrial cancer,
2.  Pelvic pain,
3.  Benign and malignant adnexal masses,
4.  Myometrial invasion of endometrial carcinoma,
5.  The normal endometrium and benign endometrium disorders,
6. Normal pelvic blood flow,
7. Uterine sarcoma,
8. Uterine myomas.  etc.