Gender scan question

Michaela • Vanessa Rose❤️ due July 11th, 2016❤ born July 5th
I was told by a friend who recently had a baby not to pee after noon bc it will be easier for the tech to tell the gender. 
Is this true? 
My appointment isn't until 3:30 and that seems like a long time for me to go without peeing with all the orange juice and water I'm drinking today make the baby active for the scan.