At this age, many full-term babies typically progress from cooing, where they vocalize with sighs and vowel sounds, to babbling, where they repeatedly use consonant sounds such as "ma ma ma" and "ba ba ba," though some will start earlier and others a little later. This is a form of vocal play, and your baby will likely get into it if you imitate the sounds back to him, which encourages him to babble more himself. If your baby isn't babbling at all by 7 months, you should let your pediatrician know. He may recommend getting evaluated by a speech pathologist, who will check for hearing impairments or oral-motor problems, which may also manifest itself as issues with swallowing or feeding. --Barbara Durkin
Originally published in Child magazine, May 2002. Updated 2009.