Why is smoking so dangerous in pregnancy?

Abruption: Smoking not only causes stunted growth in the baby, but it also causes sharp rises in the mother's blood pressure. This can cause the placenta to sheer off the uterus causing an abruption. The mother could hemorrhage and the baby's blood supply is compromised.

Damages placenta: The simplest answer is it causes the tiny blood vessels in the placenta to shrink & over time will drop the babies weight at birth by a pound. The nicotine also affects babies brain as a stimulant, causing irritability of the nervous system. After delivery, the nicotine in babies system metabolizes very slowly, taking up to 2 days to drop by half.

Fetal brain damage: Prenatal nicotine exposure increases the risk for all neuropsychiatric diseases, some by three or four fold. Tobacco smoke has increased levels of carbon monoxide and hundreds of other dangerous chemicals. These impact fetal growth and increase fetal stress.

Vascular changes: The vascular changes due to smoking decrease the blood flow and flow of nutrients and oxygen to the fetus causing an increase in miscarriages and stillbirths as well as causing growth retardation. It even increases the risk of SIDs after the baby is born.