Ultrasound Imaging: Prenatal Testing

Beaming sound waves into your womb and the surrounding areas during an ultrasound lets your doctor see remarkably clear images of your growing baby. These images are essential in checking on your baby's fetal development.

Wondering what types of ultrasounds are performed, and what your doctor is looking for in each one? Here's a primer on what you should know.

Types of Ultrasounds

Diagnostic pulsed ultrasound is safe in pregnancy for both you and your baby. Three common types of ultrasound techniques are currently in use:

• Basic, routine ultrasounds
• Targeted ultrasounds (also called level II or high-resolution): These enable sharper and more precise images of internal fetal organs, including the brain, the heart, and abdominal organs.
• Doppler ultrasound: These allow for evaluation of blood flow through the umbilical cord and placenta.

First Trimester Ultrasounds

Ultrasound (or sonar) studies can be done in any of the three trimesters of pregnancy.

Fetal Age: Routine ultrasound studies in the first trimester help obstetricians precisely determine, within about five days, fetal age through multiple measurements including the distance between the top of the head and the rear end (the crown-rump length). Measurements taken during this time provide the most accurate assessment of fetal age, as long as development is normal.

Multiples: Twins, triplets, and other multiples are detectable at this time, as is the observation that in 20 to 40 percent of very early twin pregnancies, one twin literally disappears.

Fetal Problems: Fetal death is often detected at this time, as well (when no fetal heartbeat is observed).