crown-rump length
Ultrasound measurement from the top of the fetal head to the bottom of the torso, used for accurate pregnancy dating in the first trimester.
Full Definition
Crown-rump length (CRL) is the most accurate ultrasound measurement for determining gestational age during the first trimester of pregnancy. This measurement is taken from the crown (top) of the fetal head to the rump (bottom of the torso), excluding the limbs and yolk sac. CRL measurements are most reliable between 8-13 weeks of gestation, with accuracy within 3-5 days. After 13 weeks, biparietal diameter and other fetal biometry become more accurate for dating. The measurement is crucial for establishing estimated due date, especially when the last menstrual period is uncertain or irregular.
Usage
Usage note: Hyphenate when used as a compound modifier; commonly abbreviated as CRL.
In Context
- "Crown-rump length of 45 mm corresponds to 10 weeks and 4 days of gestation." — First trimester ultrasound report