13 weeks scan and gender?

ph

I've seen loads of people and my close friend go for a scan at 13 weeks and be able to determine the sex. I've got a scan Friday which ill be dead on 13 weeks, is it possible to tell the sex? How many of you had it happened to and been correct?

I'm still going to keep my private gender scan for in 3 weeks, but just wanted to hear other people's stories...