Babies have various "I am not happy" cries, and then they have cries of severe pain and cries of terror, the latter of which normal "I am not happy" cries can progress to IMO if you are always responding immediately to terror cries, sleep training is probably fine

I didn't sleep train either of my babies and I have co-slept/bedshared with both. Most nights both kids are still in my bed. For the most part, I like this arrangement, although I am basically always underslept With future kids, I dunno. We're running out of bed lol

As a mother, I think it is very important to become attuned to and calibrated on your baby's cries, which requires trusting and consistently acting on your intuition Once, my baby was crying abnormally sharply in his car seat. I felt it was wrong. I kept driving anyway When I pulled him out, I discovered that a fairly large piece of jagged hard plastic had been digging into his back. Never again. Abnormal cries get addressed right now

To be clear, ideally whatever sleep training protocol you use *never* causes your baby to progress to cries of terror. There are many now that have tried to crack the code with check-in intervals to circumvent that It's probably best to change strategies if it happens