Ultrasound reports often include short abbreviations that can look like a secret code. These measurements are pieces of information used by your clinical team alongside your dates, medical history, and the rest of the examination.
BPD
BPD means biparietal diameter. It is a measurement across the baby’s head. It is one of several head measurements and is not meant to be interpreted on its own.
HC
HC means head circumference. It estimates the distance around the baby’s head and contributes to the overall growth assessment.
AC
AC means abdominal circumference. It is measured around the baby’s abdomen and can help your provider assess growth over time.
FL
FL means femur length. It measures the thigh bone and is another part of the growth picture.
Why context matters
Measurements are estimates, and babies grow in different patterns. A percentile or a difference from a previous measurement needs to be considered by your obstetric provider rather than interpreted from a search result. One number rarely tells the whole story.
Ask your provider which measurements are relevant for your pregnancy and how they fit with the complete report. This article explains terms generally and does not diagnose growth or health conditions.
Alison Vera, RDMS
OB/GYN Sonographer · Founder, First Hello
Alison Vera is an ARDMS certified OB/GYN Sonographer with over 10 years of experience. She founded First Hello to bridge the gap between ultrasound imaging and patient understanding.