Pyramid Approach

When the patient undergoes an examination of her unborn baby, the following question is often asked, "is my baby normal?" While there is no test that can guarantee a normal fetus, ultrasound can be used to exclude a number of serious problems. Each of the mentioned ultrasound techniques described in this section adds an additional component to the pyramid of diagnostic options. There is not one ultrasound modality that is all inclusive. For this reason, Dr. DeVore uses all of these techniques to evaluate the fetus so that he can be a thorough as possible. These techniques are used, for example, while performing a Genetic Ultrasound and a Fetal Echocardiogram. However, the Standard ultrasound examination, to be discussed later in this section, only requires the use of B-mode ultrasound. Using only this imaging technology limits or decreases the number of birth defects that can be identified during the fetal examination.

Real-Time Ultrasound

Currently, the most widely used technique for fetal evaluation is real-time ultrasound. This type of ultrasound image is displayed on a monitor and fetal motion can be observed as it occurs. In addition, movement of the heart can be identified.

Traditionally, this type of image is displayed in various shades of gray. This is called real-time gray scale ultrasound. However, a newer technique adds color to the image. This is called real-time color ultrasound. The addition of color may, in some cases, enhance the detail of the anatomy.

This is a B-Mode image of the fetal brain. The bone is white, the amniotic fluid surrounding the fetus is black, and the tissue is gray.

This is a B-Mode image of the fetal brain. The grayscale is now displayed in B-Mode color.

Real-Time Plus Color Doppler Ultrasound

This illustrates an underdeveloped right ventricle using color Doppler ultrasound.

The Doppler principle is used in many forms of science, from astronomy, to reporting weather patterns. In fetal ultrasound it is used to detect movement, primarily that of red blood cells. Therefore, the movement of blood within the heart, or other vascular structures, can be identified. The following images illustrate the four-chambers of the fetal heart, with and without the addition of color Doppler.

The image on the left demonstrates what appears to be a normal heart using B-Mode ultrasound. However, when the color Doppler is activated, tricuspid regurgitation is identified in the right atrial chamber. This fetus had Down syndrome.

All of the ultrasound evaluations performed by Dr. DeVore use color Doppler to examine the fetal cardiovascular system.

Pulsed Doppler Ultrasound

This technique examines blood flowing through vessels. During the second trimester screening examination blood flow through the uterine arteries is evaluated in order to identify those patients at risk for placental problems during the last third of the pregnancy. Abnormal blood flow patterns have a "notch" (see image). If the notch is identified during the second-trimester, I recommend the patient take "baby" or low-dose aspirin. The dosage is 81 mg. This has been shown to be safe when taken during pregnancy. The purpose for taking low-dose aspirin is that it decreases the stickiness of the platelets in the blood. Platelets can accumulate in blood vessels within the placenta and cause blood flow abnormalities, resulting in an increased risk for pre-eclampsia, growth problems in the fetus, and even fetal death.

This illustrates an abnormal Doppler waveform of the uterine artery. The notching should not be present.

Pulsed Doppler can also be used to examine blood flow within the umbilical cord. The umbilical cord connects the fetus to the placenta. In some fetuses Dr. DeVore has observed abnormal flow patterns at 20 weeks of gestation that were associated with Down syndrome, or other significant fetal problems.

This illustrates an abnormal Doppler waveform of the umbilical artery (absent diastolic flow).

Three- and Four-Dimensional Ultrasound

Three Dimensional (3D) Ultrasound

Several years ago a new ultrasound imaging technique was introduced in which fetal anatomy was examined in three dimensions. Briefly, traditional ultrasound examines only a single plane of information. This would be equivalent looking at a loaf of bread. The traditional ultrasound only examines one slice at a time. However, 3D ultrasound examines the complete loaf at one time plus it allows the examiner to evaluate an unlimited number of "slices," at various angles. This technique has revolutionized ultrasound imaging of the fetus.

This illustrates the concept of 3D imaging. When a 3D or 4D ultasound is performed, thousands of 2D images are acquired (single slice of bread) and then processed to create a 3D volume dataset. This can be displayed as a 3D image (loaf of bread).

Four-Dimensional (4D) Ultrasound

In traditional 3D ultrasound the image is "frozen" in time. When the 3D image is moving, then it is called 4D ultrasound. The fourth-dimension is time. This technique is useful when examining the fetal extremities such as the arms, legs, spine, as well as the head and face. In addition, simultaneous multiple views of the fetal heart can be viewed with this technique.

4D image of the fetal heart in which multiple views are displayed simultaneously on the screen.

4D illustrating a "blinking" fetus.

Technique Used To Examine The Fetus For Birth Defects

The technique which Dr. DeVore uses to examine fetal anatomy uses all of the ultasound technologies so that maximal information can be obtained regarding the health of the fetus.