Is it ok to smoke a couple cigarettes a day while pregnant?

NO. Pregnancy is one of the best times to kick the habit. There are many reasons to avoid tobacco smoke, and the best one of all is to give your baby a healthy start in life.
No. You should not seek permission to indulge in a small amount of this harmful habit whether pregnant or not. If two are "ok", what about three, or four, or five? Smoking is dangerous whether you are pregnant or not, but when you are, you are sharing the risk with your baby who has no choice in the matter.
No. Smoking any amount is not ok whether pregnant or not. During pregnancy you not only have your own health to worry about, but also your unborn child's. If it is only a couple cigarettes a day, you are very close to being a non-smoker-- make that final step to cut them out completely. Your baby will thank you for it.
No. I would not recommend or okay smoking at any level during pregnancy. That said, if you can at least decrease your level of tobacco use, it will benefit you and your developing baby. Because smoking is such a powerful addiction, enlist all of the family and medical support you can to help you greatly decrease or eliminate your cigarette/tobacco product use. There are programs available to help.
No. There is no known 'safe' amount of cigarettes to smoke during pregnancy. Nicotine and other toxic chemicals present in cigarette smoke have been shown to adversely affect pregnancy.