Determining the Gender by 12w?

Ivonne
Having my Sonogram in a few days, I'll be 12w3d by then. Me and my husband are always excited to see how are baby is doing. I heard by 12w doctors can determine the gender. We definitely don't wanna know at that moment since my friends throwing us a Gender Reveal party. But we def wanna see our baby! Is this true if so, should be let the doctor know before?