Crown-rump Length and Gestational Age - a Critical Appraisal of a 28 Year-Old Formula

The most accurate method of establishing gestational age (GA), other than fertility treatments, is the measurement of the crown-rump length (CRL) at a first trimester ultrasound (US). The current formula used in the majority of US machines was calculated in 1993, based on 94 women who had fertility treatments. Since that study was done almost 3 decades ago, with a limited sample size, and US machines with sub-optimal visibility, we sought to evaluate the accuracy of Daya's formula for estimation of GA, using a larger sample size.