Do doctor's use gestational age or fetal age when measuring crl (crown rump length)?

I went to my first Dr's appointment at 12 weeks 1 day (gestation) and the crl was 52.8 mm. Is that the average size for 12 weeks 1 day gestation age or 10 weeks 1 day fetal age, I'm not sure if gestational age or fetal age is used to measure crl