A Doppler ultrasound (also known as a Doppler flow study) is a noninvasive diagnostic imaging test that utilizes sound waves to evaluate blood flow through major vessels. A Doppler ultrasound is often used during pregnancy to assess the health and overall development of the fetus.
In evaluating fetal growth and development, a Doppler ultrasound is used to measure the amount of blood flowing through the brain and heart of the fetus, as well as through the umbilical cord and placenta. A Doppler ultrasound may be recommended for a mother with health issues that include blood clots, kidney or liver disease, preeclampsia or sickle cell disease.
Benefits of Doppler Ultrasound
There are many benefits associated with the use of Doppler ultrasound, especially because it is the only type of ultrasound capable of evaluating fetal blood vessels. Easily performed in a doctor's office, a Doppler flow study is considered very safe for both the mother and fetus because it does not use any ionizing radiation. In the hands of a skilled practitioner, a Doppler ultrasound's results are extremely accurate, providing information about whether the fetus has been receiving the necessary amounts of nutrients and oxygen.
Reasons for Doppler Ultrasound
A Doppler ultrasound is considered a valuable assessment tool because it detects and diagnoses potentially dangerous conditions while they are still in their early stages. A Doppler ultrasound is often performed when a fetus is exhibiting signs of intrauterine growth restriction (IUGR), which means the fetus is considerably smaller than normal for its gestational age. IUGR can cause a variety of complications for the fetus during pregnancy and delivery, and is sometimes associated with long-term health problems after birth. Some of these health risks include the following:
- Fetal anemia
- Low birthweight
- Poor resistance to infection
- Decreased oxygen levels
- Hypoglycemia (low blood sugar)
- Inability to maintain a normal, steady body temperature
A Doppler flow study may indicate that the fetus is not receiving a sufficient amount of blood, nutrients or oxygen from the placenta. If this is the case, it may result in the fetus being significantly smaller than the gestational age would suggest. A Doppler ultrasound may provide the doctor with the chance to take protective measures to ensure the baby's health throughout the remainder of the pregnancy.
The Doppler Flow Study Procedure
A patient undergoing a Doppler flow study is generally advised to wear loose clothing and remove all jewelry prior to the examination. A full bladder is recommended for this procedure to improve the imaging of the fetus, so the patient may need to drink several glasses of water prior to the test. In some cases, a Doppler ultrasound may be combined with a biophysical profile (BPP), a diagnostic exam used to evaluate fetal breathing and movements.
A Doppler ultrasound study is conducted within the pelvic region, with the patient lying on her back or left side. The abdominal area is exposed, and gel is applied to the skin to assist in the conduction of sound waves. An instrument known as a transducer is placed against the skin and moved across the abdominal area to enable the sound waves to produce images of the blood vessels, fetal brain, heart, umbilical cord and placenta, as well as all surrounding organs. The procedure is comfortable and pain-free.
The images produced by the sound waves are digitally transferred to a computer screen for the doctor to review. Using this tool, the doctor can evaluate blood flow through the fetal heart and vessels, and determine if there are any other abnormalities. The entire Doppler ultrasound procedure typically takes between 30 and 60 minutes to perform.