A: Your baby will probably master the skill of sitting up unassisted between 5 and 6 months. It's a slow process -- in order to sit up, your baby has to tackle a number of physical feats, including holding his neck steady and having control over his shoulders, lower back, and legs. At first, your baby will assume the tripod position, leaning forward on his hands for support, and over the next few months will grow steadier and steadier. By 7 months, your baby will be steadier when he sits, and may be able to hold a toy at the same time.
To help your baby practice, prop him up in a sitting position surrounded by pillows to support his back (a Boppy or other nursing pillow is great for this). You can also help keep your baby engaged (some babies don't like to sit still for too long) by giving him something cool to play with or by getting down on his level to make funny faces or sing songs.
Remember, once your baby is strong enough to maneuver himself into a sitting position, he's probably also mobile enough to tip the stroller or baby swing over. This means you need to start being extra vigilant: Always strap your baby into his stroller or swing, make sure the crib mattress is on the lowest setting and the rail is up, never leave your baby unattended on your bed or any other high surface, and remove crib toys like mobiles, which may now be within reach and pose a strangulation hazard.
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