4 to 8 Months

Your baby's muscles develop: Help him roll over and sit up.

Rolling over used to be a 4-month milestone, but now it is happening later, at around 5 months. "Because of the Back-to-Sleep campaign, babies are spending less time on their tummies, so they do not develop their trunk, or core, muscles as early. These enable an infant to roll over," explains Ari Brown, M.D., an Austin, Texas, pediatrician and co-author of Baby 411: Clear Answers and Smart Advice for Your Baby's First Year (Windsor Peak Press). So, it's a good idea to place your baby on his tummy several times a day starting at about 1 to 2 months, while he's awake and you're watching him.

Once your baby is able to roll over by himself, he probably has the motor skills necessary to clear his face if he can't breathe well while lying on his tummy. "At this point, I don't suggest that parents continually roll a baby over onto his back when he's sleeping," Brown says.

Sitting up unassisted usually occurs around 6 months, but it's fine to prop your baby up for short times before this. "It lets the baby see his world and use his hands to explore. It also strengthens his core muscles," says Brown. Babies 4 to 6 months old can be propped up between 45 and 90 degrees for 15 minutes or so at a time. Boppy pillows (boppy.com) are good for this, as is the newer Bumbo Baby Seat (bumbobabyseat.com). Just be sure to never leave your baby unattended on a couch or other elevated surface.

Tips and links by age group to help you navigate the first year and beyond.

Baby Steps
1 to 3 Months
4 to 8 Months
9 to 12 Months
1 to 2 Years