A: I think it is a mistake, though there are plenty of people who would disagree with me. But what’s done is done, and now it is going to take some time to get him used to sleeping alone. I wouldn’t let him cry too long, but don’t take him back to bed with you to get him to stop crying. Do that even once and you are back at ground zero.

If he cries before going to sleep, sit in the room with him for a little while he goes to sleep. But be sure to say, “Mommy won’t be in here when you wake up.” He is too young to understand all those words now, but I would say it, anyway. If he’s going to sleep by himself but wakes up and cries (presumably to get in bed with you), pat him a bit, perhaps give him a pacifier, and reassure him: “Mommy’s going to be in the bedroom next door, and I’ll be right here to take you out of bed when you wake up.”

If you feel too guilty doing this, remind yourself that babies sometimes become smothered when they’re in a big bed with one or both parents. He’s a lot better off in his own bed.