Accurate na mostly sa 23 weeks, mommy! A few of us tried guessing earlier pa lang and naging tama, but honestly may slight chance pa rin na magbago depending sa baby's position during the ultrasound, some babies are just shy or mahirap makita ang genitals clearly sa angle, kaya mas sure na usually sa 3rd trimester or kahit closer sa delivery! Pero at 23 weeks, yung tech usually confident na sa findings nila, so trust mo na muna ang sagot pero don't be shocked if there's a surprise lol, it happened to one of my officemate and she delivered a boy kahit they were told girl!