Mechanism of Action-

The nicotinic receptor proteins exist in human prenatal, brain beginning at 4 to 5 weeks of gestation, if a substance (like nicotine) is presented it would affect the function of the receptors in modulating dendritic outgrowth, establishmentof neuronal connections, and synaptogenesis (The formation of synapses between neurons as the axons and dendrites grow) during development.

These would lead to discoordination oftarget cell replication and differentiation. Prenatal nicotine exposure has been associated with region-specific differences (cortical greater than subcotical) in expression of the nicotinic receptor subunits nicotine stimulated catecholamine
release occurred in parallel with the ontogeny of nicotinic cholinergic receptors in the midbrain, brainstem, and forebrain during a period that corresponds to the  last trimester of human pregnancy.

Consecuences

• Spontaneous abortion
• Fetal deaths
• Neonatal mortality
• Premature delivery
• Decreased babbling in infants
• Lower quantity of cigaretts per day: Mental scores should be normal 12 months and cognitive effects disappeared by age 24 months
• 10 cigarettes or more: A four-point IQ difference
•  Higher rates of externalizing behaviors like aggressive and delinquent behavior
• Increased deficits in attention 

Causes

Smoking during pregnacy would affect the size of the baby, depends of the number of cigaretts the parents smoke or the amount of nicotine they contained.

Some risk factors are:

• Parents (both) smoke 
• High nicotine content
• Poor maternal weight gain
• Advanced age

Cigarette components:

Cigarette components:

• Nicotine
• Tar (Carbon monoxide, cyanide, cadium)

Those substances are going to make a big damage on the babies brain, pituitary and adrenalds, these these substances will be transferred from the organism of the mother to the baby through the placenta and milk