beta blockers pregnancy

Dr Specialist,
I have recently been disgnosed with partial right sided bundle branch block from an ECG trace, and am due to have an Eco and Holter monitor test in a weeks time, as per my cardiologist (which I have only just been referred to by my OBGYN). My concern is that the cardiologist wants me to start taking beta blocker "Minax" (metoprolol) before he even has the results back from these tests. I am almost 37 weeks gestation now, and have regular episodes of palpations and tachycardia daily. I do not get dizzy, or feel faint, nor do I get chest pain. I am concerned about the effects of the drug on the baby, as I have read it lowers resp rate, HR, BP & Sugars, as well as decreasing spontaneous respirations at birth in the baby. I have read the drug should be stopped 3-4 days pre labour (which I would like to know how we would know that date? as there is no elective birth planned). I am feeling I should request an early casearian (39 weeks) or an induction (if there is no risk of me cardiac arresting) and then start the drugs. I am scared of putting my baby at risk i.e. RDS etc. or having a still born due to altering its haemodynamics.
Would you mind please telling me what real effects I should be concerned or not concerned about with taking this drug.
Please provide an in depth medical explaination if you can, as both my husband and I have medical backgrounds, but not with paediatric pharmacology.
Thank you for any assistance with this if you can. I have read many journals etc. and they almost all advise against beta blockers in the final stages of gestation.
With kind regards,
K