I think the doctor has unnecessarily frightened you with this hearing. Eight out of ten people have some degree of hearing loss affecting the nerves, from very mild to severe. This is due to the modern age mechanics and the hustle bustle of the machines around us, the diet, the exposure to unwanted sounds, medications, smoking, liquor and other things.
First, please don't worry for something that no one can promise. Hearing loss does run in families but it is very difficult to predict and to avoid it. There is absolutely no need for you to fear the hearing loss getting worse or your child being born with same problem. Just relax and stay away from rumours and false knowledge on the Internet.
Ask your wife to stay away from loud sounds, ear drops, medications (without doctors advice), ear phones, noisy machines and avoid prolonged common cold.
Just visit your doctor once in 5 years and repeat an audiogram to see the status of hearing.