So my cat reacted once we had our first child. My cat is 16 years old and was very cuddly so I'm fairly sure this is part of the problem. We had noticed she had started peeing around her litter box, probably quite frequently. The smell got awful with ammonia so we did a major cleaning up of the whole area, which was a mess and not helping the situation. While cleaning, we found a white plastic bag she had peed on that had dark red urine in it. She is only peeing in the basement, not in any other room so incontinence seems unlikely.
I got her checked at the vet: urine analysis, x-ray, etc. The urine analysis showed no blood cells but was a bit clearer than normal, showing signs of early kidney failure, which the vet said is normal around this age. There were some crystals in the xray but not so much. Vet said we might benefit from another xray in a month as the crystals sometimes change position and there may be more than we know. This leads me to believe she might have had interstitial cystitis from the stress of adding the baby.
We bought a cleaner for cat pee in a pet shop and cleaned up all of the basement floor with it twice. We also got a new litter box in case that would help, bigger with lower sides. We kept both for now. I think she is peeing outside the box less often now, but still does it about once a week that we've noticed. We live in a split level and our daughter rarely ever accesses the two bottom floors so the cat uses the bedroom there most of the time to nap quietly. Our daughter sometimes hang in the kitchen where the cat's food is but it's infrequent and she's usually in her high chair.
According to questions I've read, my thinking is just to keep cleaning and maybe get a black light but I'd like a 2nd opinion on what I could do to prevent my cat from peeing around her litter box.