Dating of pregnancy using last menstrual period, crown-rump length, or second-trimester ultrasound biometry: results from the faster trial

Fetal Growth Restriction (FGR) - Identification and Management

“…This is because 'at risk' fetus is diagnosed by using a normogram based definition and the gestational age is important information for this calculation. The best method to determine the accurate gestational age is by first trimester crown rump length (CRL) using the ultrasound scan, this is accurate than the last regular menstrual date based method which is not accurate in 10-15% of pregnancies (8). Transcerebellar diameter (TCD) may be helpful in this situation as its found best to correlate with gestational age in latter trimesters of pregnancy (9).…”