smoking while pregnant

Can anyone tell me the specific affects of smoking cigarettes while pregnant? My cousin was at a family reunion about a month ago and she's in her third strimester and she was just openly smoking around everyone. What kind of damage could this cause to her baby? 
Edit: I'd also like to add that she wasn't just smoking one or two cigarettes. She went through a pack just while she was there (it was about half of the day noon to like 5)