I had sickness at least once a day for about 8 weeks with DS. Pregnant with a girl now (NHS scan plus private scan to double check) and I've had no sickness at all and I'm 28 weeks tomorrow. So I think it's rubbish.
Horrendous sickness here and having a boy. Also most of the old wives tales for having a girl have happened to me and BabyDoor is most definitely a boy. Could got have got a clearer picture of his testicles at the scan. Sonographer came across them straight away he seems to have been totally happy to show them off to us.