Gestational age from crown–rump length
Estimates gestational age from first-trimester ultrasound CRL and compares it with LMP-based age, indicating when to redate.
Calculate with transparency
Check the population, units and version. The result shows the formula or classification; it does not make an automatic treatment decision.
Preparing the form…
- Check the method
- Enter the data
- Check the result
Method · Limits of application
Robinson–Fleming 1975: GA days=8.052√CRL mm+23.73; ACOG 700/2017 redating
The Robinson/Fleming 1975 regression was fitted for 6–14 weeks of menstrual age from 334 measurements. Accuracy depends on measurement technique and calibration; the study reports estimation uncertainty, not an exact date. The local formula and obstetric redating decisions must be checked against their respective sources, without automatically extrapolating this curve beyond the studied period.
Conditions of use
Check the population, units, inclusion and exclusion criteria, and version in the original source. A result alone does not establish a diagnosis, discharge decision or prescription.
Documented parameters
- Crown–rump length (CRL) · mm
- Gestational age from last menstrual period on examination date: weeks (optional) · weeks
- Gestational age by last menstrual period: days · days
6/6 reference cases checked. Numerical tests are not clinical validation.
Relationship with cancer research
General context — relationship to be defined
A resource for general clinical contexts. This edition does not assign a specific oncological relationship; selecting it for a study requires a justified question, population and purpose.