Hi,
  Thanks  for the query. I understand your concern.  
Smoking has it's dizards in firm of allergy/respiratory disfunction in form of  
bronchitis  providing less 
oxygen & less provision for energy needed for fetal rearing. Baby is likely to  have less 
birth weight &less resistance.
    But as you have left smoking now...baby will get better energy  for rest of weeks (about 5-6 weeks)
 & will recover to some extent from the damage.
 -It will also help you in giving birth .. the delivery .
 To make up the loss you should have nnourishing diet with 
proteins (milk,pulses,non veg food except for liver)/vitmines&minerals  (plenty of salads,fruits .
    Take B complex,vitamin Esuppliments along with routine calcium &iron .
      Do not ever try yo smoke again... not while the baby iß by your side,for  the indirect inhalation of dmoke would dsmage babies respiration .
    Take care   thanks.