Does serve morning sickness affect the size of your baby when it's born?

Im 6months pregnant with my 1st child. My morning sickness has only just eased up. Im still struggling to eat things i use to but am managing to keep alot more down. Some days easier then others. But in total i lost 8kgs from being sick and have now gained 6 of those kgs back. So technically speaking im 26 weeks pregnant and havent put any weight on. Everyone keeps telling me because i was so sick it would affect the rate of the baby's growth and i would end up giving birth to a 7lber or less? Is it possible or does it have nothing to do with it.