I think it has something to do with the liver transforming nicotine into a carcinogen and then transferring it to the baby.
I don't remember how the circulatory system works, but if anything the liver should be the one place that would sort out all the kwap from the baby. I only remember that blood travels unoxygenated until, where, the vena cava? I forget.
"Pinkerton's group had previously shown that rats exposed to secondhand smoke while in the womb and after birth developed hyper-reactive, or "ticklish," airways, which typically occurs in children and adults with asthma."
They are saying a 'direct exposure' to the unborns lungs.
Not possible.
Why would 'ticklish' airways develop in an unborn rat?