Hello, My 4.5 month old has started rolling onto his tummy in his sleep. He is in a sleeping bag with his arms out and sleeps in a cot in our bedroom. Do I need to roll him back over onto his back? I’m worried that he’s still at an age where SIDS is a higher risk which terrifies me. He also struggles to roll himself back into his back. Thank you!

What you are describing is normal development.
Most babies will be rolling over by 5 months…....some earlier, some later.

This is very normal as babies grow & become stronger many babies then prefer to sleep on their tummy, & often don’t change from that position.

This is not something that needs to be stopped, but it is important to make the environment as safe as possible for this to occur.

Always place baby on their back to sleep.
Ensure cot mattress is firm, well-fitting & flat.
Ensure there is nothing loose or soft in the cot.
Use a sleeping bag now that has appropriate size neck & arm holes.

Red Nose has the following information now that your baby is starting to roll.

Give baby extra tummy time to play when awake and supervised as this helps baby to develop stronger neck and upper body muscles which in turn enables them to roll back over.
Make sure that baby is on a firm and well-fitting mattress that is flat (not tilted or elevated).
Make sure that baby’s face and head remains uncovered (do not use lambswool, doonas, pillows, cot bumpers or soft toys)

As babies grow and develop they become very active and learn to roll around the cot.
At this time, continue to put them on the back at the start of sleep time, but let them find their own position of comfort.
By this stage it is not necessary to wake during the night to turn baby over to the back position

Do not use any devices designed to keep baby in a particular sleep position.
https://rednose.com.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over
https://rednose.org.au/article/is-it-safe-to-use-products-designed-to-keep-baby-in-a-particular-position

If you are concerned about his rolling back, it may be helpful ti increase tummy time while awake.