So it turns out my baby's hearing loss is caused by CMV. It's like a 1 or 2% of the baby getting it from the mother, pretty rare for a virus that almost all of us have contracted. Of that tiny percentage almost all babies will be like Walter, having slightly impaired hearing, and then a few unlucky ones can have a host of horrible symptoms including malformed brain, blindness, kidney and spleen failure etc. Thank goodness Walter is not one of those and that goodness I have an ultrasound from the day he was born confirming that his brain is all correct, so that there's no need to try to do an MRI on the little guy. He's now on some sort of retroviral medication that is ruinously expensive without insurance, so I'm very thankful that I have coverage, even if I am reminded again at how crazy the system is. (the insurance company will give me a bigger discount if I buy a 90 day supply at one time, except the medicine expires after 45 days...). The meds will keep his hearing from getting worse and potentially even reverse the effect. The only bad part is that they might mess with his immune system, which originally I found worrying, but the doctor told me dryly that all babies have pretty crummy immune systems, so I don't have to be any more careful than I would if he wasn't taking the medication. I guess you can take that how you will depending on if you're a glass half empty or full kind of person. For me, I'm very glad that while the medicine is fussy, the whole thing just isn't that big a deal.