Join Us for the 49th Annual OB GYN Conference in Orlando, FL, February 11–14, 2026. Register now!

Do You Know Everything You Need to Know About the BPD Level?

October 27, 2011

The AIUM Practice Guideline for the Performance of Obstetric Ultrasound Examinations recommends that the biparietal diameter/head circumference (BPD/HC) measurement be taken at the level of the thalami and cavum septi pellucidi (CSP).

Which image below shows the CSP?

 

Answer:

The CSP is seen on a sonogram as an empty box (image on the right), and the columns of the fornix have a line going through the box (image on the left). Although the columns of the fornix and thalami are still accurate levels for the BPD/HC measurement, you lose the diagnostic information that a normal CSP would demonstrate. With a normal CSP a midline brain defect can be ruled out.