just wanted to add also that the drugs are classed differently in pregnancy than in breastfeeding. One I am currently on is rated B for breastfeeding but D in pregnancy.
From what I understand a status of D means that if the benefits greatly outweigh the risks and taking an alternative medication is not an option, they you might still take it.
Oh, and I 2nd that mothers matter website. It is updated regularly and the people who give the information for it are really experienced