Internet research tells us that smoking during pregnancy
can harm your baby. The rates of SIDS, behavior problems,
learning disabilities, and low IQ. These are due to
the fact that the cigarette smoke flow replaces the oxygen
flow to little fetus' brain.

It also increases the chances of deformity and other
birth complications.
This warning doesn't really deserve to be killed... but some if it does get a bit on the excessive side. Some of the propaganda accompanying this subject depicted the wholesome scene of a mom, naked & pregnant, hand on her giant tummy, suckin' back a Marlboro. Not really necessary or effective.

Maybe it's optimism, but it seems that it's enough in the public eye these days that fetus smoking is bad... they plug this crap, while other more important stuff goes ignored.