Alcohol consumption leads to Fetal Alcohol Syndrome.
Pain pills, heroin, methadone and Suboxone
, if not tapered during pregnancy, will leave the baby addicted at birth.
Cocaine use can lead to insufficient blood supply to the baby and death of the fetus in the womb.
If you quit before you are pregnant, none of these will be a concern. You will not have to worry about telling anything to the obstetrician or midwife, and you will not have to worry about what they may suspect.