During the course of her prenatal visits, a pregnant woman will likely encounter a few different Doppler tests. While it is sometimes used as part of a more comprehensive exam, Doppler technology can also be used alone. Doppler testing helps doctors to diagnose problems and make decisions about potential interventions in a timely manner.
Mechanism
Doppler technology works by sending directed sound waves into the abdomen of the pregnant woman. Using a principle called the Doppler effect, these devices can detect changes in movement, not merely imaging static structures as traditional ultrasound does. The machine works by detecting the slight differences in the returning sound waves as they bounce off fetal structures.
Types
There are several types of doppler tests and devices used in pregnancy. Doppler sonography uses the same device as an ultrasound but measures blood flow in the baby's body, placenta and umbilical cord. A transvaginal Doppler probe is placed in the vagina of a pregnant woman instead of being held on top of the belly. A Doppler heart monitor uses Doppler technology to listen to the baby's heartbeat from outside the womb without providing a visual picture.
Purpose
In early pregnancy, a transvaginal Doppler can be used to observe the growth of the baby or diagnose potential problems when the fetus is still too small to be accurately observed using traditional ultrasound. Throughout the pregnancy, Doppler heart monitors are used to listen to the heartbeat of the baby, which sounds like a galloping horse. A Doppler test can be used during the third trimester to pinpoint problems with blood flow, especially in mothers carrying multiples or whose baby is experiencing growth restriction.
Advantages
One advantage of using Doppler sonography for diagnosing problems in pregnancy is that this technology is noninvasive. Doppler technology is capable of much greater resolution than traditional ultrasound alone. The use of Doppler testing allows doctors to observe and monitor the developing baby much earlier than other technologies. For example, according to Obstetric Ultrasound, a baby's heartbeat is detectable using fetal Doppler testing by the sixth or seventh week of gestation.
Considerations
Because the safety of Doppler technology is unestablished in early pregnancy, its use is generally reserved for when the doctor suspects that there may be a problem. According to Science Daily, some doctors have expressed concern that Doppler sonograms may cause unnecessary interventions. However, the same report also indicates that because of the use of Doppler ultrasound, the rates of Cesarean sections and infant and fetal death have gone down. Doppler tests may also be expensive, especially when used repeatedly throughout the pregnancy.
