Those are questions you must discuss with your doctor - what doctor put you on your heart medications?
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There are a number of beta blockers that can be used during pregnancy and postpartum. Many of them pass into the milk, but at levels so small that they are not a concern. I strongly recommend using Google to browse the teeming online articles available on this as well as the use of other specific beta blockers. While it's good to educate yourself on this subject, consulting with your physician is best. I can tell you this about Metoprolol. It is eliminated very quickly from your blood, and there is no specific rebound effect from stopping it. Within several days of ceasing it, the drug will be eliminated from your body.
Thank you. It was my cardiologist that put me on the heart meds and she specializes in pregnant women with heart conditions.