Doppler Scan During Pregnancy

Doppler scan is performed usually during the third trimester. But in certain circumstances like multiple pregnancies and other significant instances, it is performed during the second trimester. In some cases (like high risk pregnancies) more than one Doppler scan will be conducted by the doctor.

Is Doppler Scan Safe During Pregnancy?

Yes. In the same way as with all ultrasound scans, if utilized appropriately, Doppler scan presents no danger to your child in the second and third trimesters. On the other hand, it actually helps to identify a high-risk pregnancy, thereby, reducing infant death, possibly through better timing of C-section or induced labor.

When Does the Doctor Recommend a Doppler Scan During Pregnancy?

The doctor will recommend a Doppler scan when complications or abnormalities are identified during earlier scans, emphasizing the need of extra care for the expecting mother in the course of pregnancy. The high-risk pregnancies are generally assisted by the Doppler scans. Some of the conditions for which the doctors recommend Doppler scan are:

1. Multiple Pregnancies

If the mother is carrying more than one child the pregnancy is considered as high- risk, as there are several possible complications such as Intra Uterine Growth Retardation(IUGR), Twin To Twin Transfusion syndrome(TTTs), cord entanglement etc. Therefore Doppler scan is unavoidable as it enables early recognition of possible issues.

[Read : 10 Potential Complications With Twin/Multiple Pregnancies]

2. Health Conditions of the mother

There are several factors which affect the ‘low resistance’ property of the umbilical arteries. (The low resistance property provides easy flow of blood through blood vessels). Lifestyle factors like smoking, intake of alcohol, intake of certain medicines, etc. will increase the resistance of arteries thereby affecting the flow of blood. An expecting mother should undergo a Doppler scan if:

• She has a history of losing the baby at birth in the previous pregnancy.
• Already experienced a late miscarriage.
• Has a history of carrying a growth restricted baby.
• If the frequency of the fetal movement decreases.
• If subjected to medical conditions such as high blood pressure or gestational diabetes.

3. Health Conditions of the Fetus

Doppler scan is recommended if:

• If the fetus affected by rhesus antibodies.
• If the growth rate of the baby (in previous scans) are not satisfactory.

[Read : Slow Fetal Growth During Pregnancy]

4. Placental Problems

The placenta is essential for the baby’s healthy development because it supplies the fetus with blood, oxygen, and nutrients from the mother’s body. During the anomaly scan in the second trimester, if problems or irregularities such as slower fetal growth is noticed, a Doppler scan will be scheduled in order to check if the placenta is working properly.

If placenta previa (low lying placenta) is detected, then a Doppler scan is scheduled to check the position of the placenta before the due date as the Doppler scan shows the change of placental position which can occur towards the end of pregnancy.

How is A Doppler Scan Different From Usual Ultrasound Scan?

Both Doppler and normal prenatal scans use ultrasound waves. Therefore, as far as the expecting mother is concerned, there will be no difference. Also, the procedure of the scanning will also be the same. The only difference is that in Doppler scan high-frequency ultrasound waves are used which project into the uterus and are echoed back to the transducer, bounce off the RBC (red blood cells) as it moves. This helps to calculate the rate of blood flow through the umbilical cord and other blood vessels and also in identifying the blocks in arteries and reduced blood flow (if any).

Whereas, in normal ultrasound scan the frequency of sound waves will be lower than that of Doppler scan and even though it bounces back from the different tissues at different rates determining the shape, size, and structural abnormalities (if any) of the fetus, these low-frequency waves are not able to bounce off the small sized red blood cells.

Which Areas Are Usually Checked With Doppler Scan During Pregnancy?

In general, Doppler scans examine whether a fetus is developing healthily by examining the flow of blood between the mother and child. Whatever it may be, the doctor may ask the sonographer to check different areas depending on the concerned factors which make him decide to go for the Doppler scan (which can vary with each pregnancy). Here are a few types of Doppler scan usually conducted during pregnancy.

1. Uterine Artery Doppler Scan

Uterine arteries are blood vessels which take blood to the uterus. Normally these arteries are small in size. But in the course of pregnancy these arteries increase in size (stretches) to providing less resistance and thus allowing more blood to flow through it. The Doppler scan in this area helps to check whether enough blood is reaching the womb.

2. Umbilical Artery Doppler Scan

In umbilical artery Doppler scan, the blood flow from the baby through the umbilical cord towards the placenta is checked. This scan helps to make sure the baby is getting everything he needs from the mother’s placenta. The umbilical artery Doppler scan is performed if the mother is carrying more than one baby or if the growth rate of the baby is less for the gestational period or if the baby is affected by rhesus antibodies.

3. Middle Cerebral Artery Doppler Scan (MCA Doppler Scan)

If some issues are detected during umbilical artery Doppler scan, MCA Doppler scan is performed to check the blood flow in the baby’s brain.

4. Ductus Venosus Doppler Scan

This scan is done if the first result of any of the above scans shows issues. Here, the blood vessel which carries well oxygenated blood from the umbilical vein to the heart of the baby is assessed to evaluate the volume of blood reaching the baby.

Read Also: What Prenatal Tests are Done in the Third Trimester?