"Gas is often caused by swallowing air," notes pediatrician Jennifer Gardner of Healthy Kids Company, an online site devoted to child wellness. "A crying baby takes in air as he cries, so try to feed him before he becomes inconsolable," she recommends. Keep the baby's head higher than his belly while nursing, Gardner advises. Burp him in an upright position every five to 10 minutes while feeding and again immediately after. "You want to be sure you hear the burp -- this means air taken in has been released," she explains. Certain foods, including dairy, legumes, cruciferous vegetables, bananas, and onions, also can cause your baby to be gassy, she says. "If you think this is a possibility, discuss it with your baby's pediatrician before making any major changes to your diet," she advises.