Even if fed properly, both bottle fed and breast fed babies usually swallow some air. Holding the baby upright over your shoulder and then patting or rubbing his back usually helps bring up the air. The baby may also be burped by holding him in a sitting position and placing him face down over your lap and gently rubbing his back. It is not always necessary to interrupt a feeding to burp the baby but should be attempted after each feeding. Of course babies do not always burp and you should not try to force it, but you may try again 15 to 20 minutes after the feeding.