Is it safe to use niaspan (niacin) while pregnant?

Yes. Niaspan (niacin) is a slow release formulation of the vitamin Niacin which is safe to use when pregnant and is included in much lower amounts in prenatal vitamins.
Depends. Niaspan (niacin) used in normal amounts as part of a multivitamin is considered a category a or the safest medication category during pregnancy. If used at higher levels like those suggested to treat lipid disorders it moves into category c. That means that animal studies have raised some concerns but human studies have either not shown problems or are not broad enough to keep it in a safer category.