No and yes. Not safe for pregnant women ("possibly hazardous") it is safe during lactation even for the newborn.
Dilantn. Fetal hydantoin syndrome is a syndrome of birth defects that happen in babies born to moms who take dilatin during pregnancy. Caution is advised for breast feeding moms on taking dilantin.
Yes. This drug is usually used for seizures. It is a category d drug which means there may a chance the baby could be affected by the drug. However, not taking it and risking a seizure while pregnant is also bad for the baby. If your doctor prescribes this drug, you will need more Folic Acid than others and extra vitamin K in the last month of the pregnancy.
No. But it depends. It may be safer to stay on it than stop if that is the best drug to control seizures. It is a class d drug, meaning there is evidence of fetal risk, but the need to adequately control seizures may outweigh this risk. Discuss this with your doctor. It is considered compatible with breastfeeding by the american academy of pediatrics.
Pregnancy Category D. While Dilantin is considered a safe drug during breast feeding it is considered toxic to a fetus. Growth deficiency, decreased mental performance, changes in facial features and various other anomalies have been recorded.
Better options. Dilantin is a drug of the 1930's and has been supplanted by numerous more effective and safer medications. Does possess teratogenic potential, and does cause osteoporosis, and liver and bone marrow issues in many. Levels change meteorically in pregnancy, and tough to keep in therapy range. However, a convulsion could cause miscarriage. Would get a different med asap.