Another thread on MN made me think of this - What's the best old wives tales you've heard RE: pregnancy?
Most common whenever I mention my hellish heartburn is, 'ooh your baby will have lots of hair when it's born'
More randomly I've been told that when carrying a boy then the shape of your nose changes/gets bigger. If carrying a girl then you're not as pretty as 'she steals your beauty'.
Any other funny/good ones?