I'd start buying pink stuff!!!! If your gender determination was at 20w, you can be pretty certain that it's accurate, it is more when determination is made in the early 2nd trimester, that it can be a bit hard to tell for sure. I had my determination made at 19w with my oldest daughter, and it was obviously right... and with this one (a girl) it was made at 19w & then again at 23w, and both times it looked VERY convincingly like a girl. I think they just can't say "I'm 100% sure" incase it turns out to be long & their are repercussions for them.