Is it safe to let my baby sleep on his stomach?
Generally, no. It is not safe. You should always put your baby down to sleep flat on his back on a firm surface. Things like soft mattresses or other bedding, pillows, couch cushions, or nursing pillows are not safe for sleeping in general – this is especially true when he is on his stomach. Know, though, that once your baby can roll over on his own, that you do not have to worry about him sleeping on his stomach when on a flat surface without pillows or soft bedding. In other words, once he can roll over, there is no need to worry about turning him back over onto his back during the night. This is especially the case if he can go from his back to his stomach then return to his back all on his own. If he still needs some practice with this last skill, go ahead and practice with him during the day.
About Dr. Erin Leichman