How does smoking affect the placenta?
It is likely that chronic exposure to tobacco constituents in early pregnancy can affect placental development directly or indirectly by reducing blood flow, which creates a pathologically hypoxic environment. From an abstract in PubMed.gov. This environment will produce a child that is underdeveloped.
Other problems are:
premature rupture of membranes
cerebral palsy (a set of motor conditions causing
mental retardation and learning problems
an increased risk of death
Sudden infant death syndrome (SIDS)
Just think of the cost to you, the baby and the rest of us if you make this choice.