Finding out gender at 13w

So I didint know you can see anything so early on but recently I've been seeing some mamas show off their babies and how they can see the gender of the baby around 13w some even around 12w so I'm wondering for those of you who had a scan that early and if you thought you knew the gender was it correct ? I know it's better to wait around 20w but I'm just so anxious to find out. My last pregnancy I found out at 18w and that was my 2nd scan(first being around 8w) so I couldn't be able to compare my son's us to this new little baby