Smoking can affect your pregnancy quite a bit because you are exposing your baby to harmful chemicals like tar, nicotine and carbon monoxide. Other than that, it can reduce the amount of oxygen that can damage baby's growth and lungs...That are so many more negative side effects and no positives...
Not to mention the fact thanks the all those toxic elements, your baby can be born already going though withdraw. Which create more issues in your babys health, mood, breathing, and growth. So please avoid smoking at all cost