Career vs ttc

My husband and I have a 10 1/2 year old daughter.  In October 2015 we decided to start ttc again.  We got pregnancy in November but unfortunately in January we had a miscarriage.  In January I was offered a huge promotion with my company which has been a huge blessing financially.  Unfortunately with my new position I would be unable to work while pregnant(per my doctor-it is unsafe).  We want another baby so bad and I am at a crossroad- do I talk to my boss beforehand(we are very close, and he knows what I went through in January), or do we just go for it and address it once I am pregnant?  I am fairly certain my position wold be held for me, but not sure they could accommodate me to continue working throughout pregnancy-which would be the perfect solution if they could.  I am so confused on what to do here.  Any suggestions?