I think it is really 'luck of the draw'. My mum had none, niether did I or one of my sisters but the other basically threw up 24/7 for the whole nine months each one. She had two girls & I always thought that maybe a girl messed with you a bit more because of 'clashing hormones' but seeing as plenty of women have no morning sickness with girls then that doesn't make sense either.

All I can do is pray that my good luck stays with subsequent pregnancies.