What are the risks of getting pregnant after open heart surgery (vsd repair, it has only been three months)?

Depends: Consult a perinatologist and you cardiologist regarding what category of heart disease. Also ask about vaginal versus cesarean delivery. With some cardiac problems, cardiologist suggest elective cesarean at term to avoid "pushing" and increased strain on the heart.

Heart damage: Likely it is possible but if you have significant cardiomyopathy or pulmonary hypertension then it could be risky and dangerous. Check with your cardiologist or surgeon before actively pursuing pregnancy.