I wouldn't like to seem categorical but I dream of all pregnant women stop smoking from the very first day or as early as possible.
I have a friend and her child is 1.5 year old. He is healthy and happy child but…
When she was pregnant she smoked, "less than usually and nothing dangerous" as she used to say (all women say so).
The baby was born and there were a lot of problems with his lungs, he couldn't breath for a long time. The doctor talked to my friend and when she told him about smoking everything became clear at once. He said they could avoid a lot of problems with the baby's health, if she didn't smoke. I remember she told me: "I was ready to kill myself for it, I hardly lost my baby and I still feel guilty".
Even now when you read this I am sure you smile and think: "It is just one case, it will be different with me, maybe doctors just try to hide their own mistakes here and something like that", probably, but I will never forget that talk with my friend and her