A: Marlena, it's good that you put your baby to sleep on her back. You should continue to do this for the first year of life to help prevent smothering and reduce the risk of SIDS (Sudden Infant Death Syndrome) by nearly one-half.

It's also a good sign that your baby's beginning to roll over. Most babies start rolling over between 4 and 6 months of age. This shows that your baby is developing strength and coordination in her head, neck, upper body, arms and back. While it's natural for you to be concerned about her rolling onto her tummy during sleep—and it's good for you to check in on her when you go to bed to make sure she's on her back—experts don't recommend that parents constantly monitor their babies all night. In fact, babies are most at risk for SIDS under the age of 4 months, before they have much upper body strength and are able to lift up their head and roll over. If your baby were to roll over onto her stomach, her increasing upper body strength would help her turn her head to breathe and stay safe.

A recent study found that babies who have experience on their tummies during waking hours develop better upper body strength and head-turning skills, and are at lower risk for SIDS. Be sure to give your baby active tummy time a couple of times each day when she's rested, fed, calm and alert. Here are some fun ideas:

• Lie on your back with your baby on top of you, tummy down, with her head on your chest. Talk and sing to her. She'll want to pick up her head to see you and play with your face.
• Lie on your back with your knees up and your baby tummy down along your shins, with her head at your knees. Hold onto her and bounce your legs gently up and down. Talk and sing to her, and bring your knees and head forward to kiss her.
• Lay your baby on her tummy on the floor, with a small cushion or rolled up towel under her chest to prop her up. Lie down in front of her to play with her, and set out toys within her reach. Try to encourage her to push up with her arms by showing her interesting things above her head, such as your face, a mirror, a rattle or a stuffed animal.
• Place your baby tummy down on a blanket. Lift up the front two corners and pull her around the room making motor sounds.
• Consider getting your baby an infant activity mat designed for tummy-time play.