Severe problems! Crystal meth can cause poor growth due to restricting blood flow to the placenta. It can cause premature separation of the placenta with bleeding, premature birth and possible bleeding for the mother and baby. There is a risk of both maternal and fetal death. Meth may also cause later brain problems for the baby. There is also possible risk from lifestyle issues for women using illegal drugs.
There are many. There can be brain altering/damaging effects that cause developmental delay. Heart attack, stroke, paranoid psychosis, abuse dependence, severe mood changes. Dental problems - tooth decay known as "meth mouth". A parent abusing meth will not be able to provide a child a safe and healthy home environment and subject child to emotional (and physical?) abuse.