Crown-rump length
Measurement from the top of the fetal head to the bottom of the torso, used for gestational age assessment in first trimester.
Full Definition
Crown-rump length (CRL) is a standardized fetal measurement taken during first-trimester ultrasound from the longest straight-line distance between the crown of the head and the rump. This measurement is considered the most accurate method for establishing gestational age between 6-14 weeks of pregnancy. CRL measurements are critical for dating pregnancies and establishing baseline parameters for subsequent screening tests. The measurement must exclude fetal limbs and is typically recorded to the nearest millimeter.
Usage
Usage note: Often abbreviated as CRL in clinical documentation. Hyphenate when used as adjective modifier.
In Context
- "The crown-rump length measurement of 23.4 mm corresponds to 9 weeks 2 days gestational age." — Ultrasound report
- "Dating accuracy decreases after 14 weeks when crown-rump length is no longer the preferred biometric parameter." — Clinical guideline