Why is Smoking Increases the Risk for Placenta Previa?

Because cigarette smoke is a cocktail of toxic sh*t which f*cks up so many biological pathways that the list of sh*t that it does will never ever ever stop growing.

That above statement will mean SOMETHING to anyone, but you may not really comprehend what I mean by it unless you have medical training. Think of like this: most drugs these days are (ideally) designed to target a particular protein, or act on a particular pathway. Thus, it may have side effects but it generally wont interrupt TOO MANY different pathways (although it might interrupt a few). But honestly, there is barely a pathway in you’re body that isn’t in some way effected by smoking. Possibly noone can pin-point the exact reason why it increases the risk of placenta previa, but there may not be a single reason – it's just a combination of things.

N.B You should be punished severely by the law for smoking while you’re pregnant anyway. It’s child abuse. It’s one of the worst forms of child abuse too. How will you feel if you’re child is born with a congenital disorder which YOU caused? Or more the point, how will you’re child feel having to live with it? And you can argue that it’s your choice all you want, but personally I don’t see why you should have the right to CHOOSE to do that to your child anyway. I honestly think the law should step in and stop you. That’s what the law is meant to be there for (to protect those who can’t protect themselves).