I had open heart surgery how will this affect me having birth?

Depends: What was the operation? Some are cured and no issues. So your surgeon or cardiologist need to help, you decipher the risks of fluid retention, cardiac stress, delivery etc. In your personal situation.

At 34 y/o : I am guessing your open heart surgery was to repair a congenital structural or conduction defect. If the repair was successful and you are not in any drugs like warfarin or any other i think you will not be affected for having birth. But, this have to be discuss with your cardiologist in coordination with your obgyn. Good luck.