One last cigarette, another weekend of binge drinking or your umpteenth stop at a fast food restaurant can all have a negative effect on your developing child and it's best to take the time before conceiving to break yourself of these habits. (mypregnancyguide.com)
if you can not control yourself, build in a gap of at least an hour between your last cigarette and your next feeding session so that the nicotine in your system has a chance to decompose at least partially. (verywellfamily.com)
The advice is to give up smoking during pregnancy and breastfeeding, or at least to limit the habit as much as possible, extend the time between the last cigarette and the baby's feed, use nicotine patches, smoke outside the house and avoid smoky environments. (sciencedaily.com)