CRL (Crown-Rump Length) Calculator

Clinical accuracy in early pregnancy dating relies heavily on the Crown-Rump Length measurement. This metric remains the gold standard for establishing the Estimated Due Date during the first trimester. Errors here propagate through the entire pregnancy timeline. They affect screening windows for aneuploidy and decisions regarding induction.

This tool utilizes regression models from the Fetal Medicine Foundation and Intergrowth-21st standards. It converts measurements in millimeters into a precise gestational age in weeks and days. Unlike basic calculators that output a single date. We provide a confidence interval. This manages patient expectations regarding biological variability.

The calculation relies on the Robinson and Fleming non-linear regression model. The basic relationship between Crown-Rump Length L and Gestational Age T follows this curve.

Where L represents length in millimeters and T represents time in days. Biological variance implies a standard deviation σ which typically expands as pregnancy progresses. We apply a fixed range for simplified reference.