Which gestational age should be taken as correct if the known dates are different from the weeks by exam score?

"The examination is, by validation studies, accurate within 2 weeks of known dates. Since maternal ovulation can vary over 10+ days, we consider agreement within 2 week between dates by last Normal menstrual period and exam to be closest to dates. If the difference is greater than 2 weeks, then the exam is taken as the gestational age."

Dr. Ballard

References :
Ballard JL, Khoury JC, Wedig K, et al: New Ballard Score, expanded to include extremely premature
infants. J Pediatrics 1991; 119:417-423.