There's no law against smoking while pregnant.

However, your right to smoke ends when it affects someone else. If you smoke in a hospital room which contains a lung patient, you can be removed from the room (and probably from the hospital grounds). Each time you smoke a cigarette, you are affecting the health and growth of your fetus. Now, if you plan to get an abortion, then smoke away. If you'd prefer to carry the pregnancy to term and have a healthy baby at the end of it, though, you're not optimizing your chances. Babies of smokers tend to be sicklier than babies of nonsmokers.

Oh, and you might want to look up how long it takes to deliver a baby. I believe it's something like 18 hours (possibly more) for first time mothers. They aren't going to let you have a single cigarette during that time, nor will they let you have nicotine gum or patches.

And what are you going to do when you have the baby? Gonna smoke around it?