Background: A fetal ultrasound [US] scan during the first trimester of pregnancy is essential for confirming fetal viability, estimating the fetus' gestational age [GA], and identifying fetal anomalies. US pictures taken in the first trimester of pregnancy seem different from those taken in the second trimester because of the distinct developmental stage of the fetus.
Aim of the Study: To compare between 2D US and 3D US with regard to CRL and E/FV in an accurate estimation of GA in the first trimester.
Patients and Methods: This prospective research was done on 48 cases of singleton live pregnancies at 7–11 weeks' gestation in the department of Obstetrics and Gynecology, Al-Azhar University Hospital [New Damietta] from January 2021 to January 2022.
Results: There was a significant positive association between embryonic volume and embryonic CRL in the 8th, 9th, 10th, and 11th weeks. However, there was no significant correlation in the seventh week. This means that the calculated gestational weeks by CRL and VOCAL are close to those detected by LNMP. The diagnostic accuracy of CRL in the detection of fetal age was higher than the accuracy of VOCAL in the detection of fetal age as compared to LNMP. 
Conclusion: The use of E/FV for GA determination is nearly as accurate as CRL, despite the fact that it is less complicated and relies on 2D rather than the more expensive and complex 3D US. EV/FV is a good predictor of GA and new, promising technology.