My wife has a issue going in that she requires surgery for. If she were to get pregnant it could potentially kill her and the baby. Am I allowed to use a condom to make sure to prevent it ?
Using a condom is considered haschosas zera, (wasting seed) and halachically the worst type of type of contraceptive. There are many different types of contraceptives nowadays, including, pills, foam, IUD, tying of the fallopian tubes, etc. Check with your doctor if there are any other types of contraceptives that can be used- they are all better than using a condom. If medically nothing else is acceptable, let me know.