During an ultrasound exam, high-frequency sound waves are used to create a picture (sonogram) of the baby and placenta. A hand-held ultrasound probe (called a "transducer") is moved over your abdomen (or placed gently in your vagina, for a vaginal ultrasound). An ultrasound exam does not use radiation (like x-rays) and is not known to cause any harmful effects in either the mother or the baby.

Ultrasound Exams

The ultrasound will be used for two different types of measurements. The abdominal ultrasound (or possibly vaginal ultrasound for the first two visits) will be used to measure the size of the baby. These measurements include:

• Abdominal Circumference (the size of the fetus around its middle)
• Biparietal Diameter (BPD; the width of the head from side to side)
• Crown-Rump Length (the distance from the top of the head to the base of the back)
• Femur Length (the length of the long bone in the upper part of the leg)
• Head Circumference (the distance around the head, at the widest point)
• Occipitalfrontal Diameter (OFD; the size of the head from back to front)

Doppler ultrasound (commonly used to listen to a baby's heartbeat) will be used at the same time in order to measure the blood flow to the placenta and the baby.

For more information, check out the U-M Health System page on ultrasound exams.