My moms going to be disappointed

So we have had multiple ultrasounds around the 20w anatomy scan and baby wouldn’t show what gender it was. I went and got the sneak peek and it said it’s 99.6% effective if taken this late in pregnancy. Got the results in last night and it said boy!! Totally threw me as I was thinking girl, I think mostly because that’s what EVERYONE has been telling me I’m having.

Well now I’m concerned about telling my mom as she was so excited for a baby girl, I was saying something the other day about the nurse at my appt and she thought I said baby was a girl and actually started crying with happiness. I know there is the possibility that there was contamination and the results could be wrong. My next ultrasound is on Jan 29 and I’m wondering if we should wait to tell her until we can confirm. But it’s so far away!

Edit: just wanted to add that I’m in Canada and private ultrasound places are rare near me and super expensive. Also I am thrilled to be having a boy as I already have a much older child that is a boy so I feel more prepared