FL
Also written as: FL — Femur Length
Femur Length - measurement of the fetal thigh bone used for gestational age assessment and growth evaluation.
Full Definition
Femur Length (FL) is a standard biometric measurement in obstetric ultrasound, representing the length of the fetal femur (thigh bone) from the greater trochanter to the external condyle. It is one of the four key measurements used to estimate gestational age and fetal weight, along with biparietal diameter, head circumference, and abdominal circumference. FL is particularly useful in the third trimester and can help identify skeletal dysplasias or growth abnormalities. The measurement should exclude the distal femoral epiphysis when present in the third trimester.
Usage
Usage note: Always measure the ossified shaft only; exclude femoral head and distal epiphysis when visible.
In Context
- "Fetal biometry showed FL of 65mm, consistent with 34 weeks gestation." — Third trimester ultrasound
- "The FL measurement was significantly below the 5th percentile, raising concern for skeletal dysplasia." — Detailed fetal anatomy scan