Midwife said to get ultrasound when I'm 20 weeks. Would it be okay to get it on 19 weeks?

El
I'm having a gender reveal party on the 7th of April because the next weekend is Easter weekend. My midwife said to get the ultrasound between the 10th and 14th but I wanted to do the reveal party the same day as the ultrasound. Would it be fine to find out the gender during 19 weeks instead of 20? Will it show?