Most recommendations on reducing the risk of SIDS say that you should have LO sleep in your room, separately, the first 6 months. I imagine if you wanted to sleep train at around 4 months, it would be really hard with LO crying in the same room, and knowing you are right there! Most CIO methods include some sort of soothing without picking up, or picking up and putting back down without feeding, and then leaving the room. So I guess you could sleep train and spend much of the night in another room until LO is a good sleeper? Or is it impossible?