Safe sleep is one of the most important topics for new parents, and the choice between a sleeping bag and a traditional blanket is a question that genuinely matters. Here's what the evidence says — and what to look for when choosing.

The way your baby sleeps in their first months has a significant impact on their safety. Both the NHS and the Lullaby Trust have clear guidelines on creating a safe sleep environment, and understanding these guidelines is the starting point for choosing between sleeping bags and blankets.

What the NHS and Lullaby Trust Recommend

The Lullaby Trust, which is the UK's leading charity for safe sleep research, advises that loose bedding — including blankets, quilts, and duvets — should not be used for babies under 12 months. The reason is that loose items in the cot can cover a baby's face during sleep, potentially causing overheating or restricting airflow.

Baby sleeping bags are recommended as a safe alternative because they are designed to stay in place. A well-fitted sleeping bag cannot ride up over a baby's face, and because both arms remain out and free, the sleeping position is not restricted.

Understanding TOG Ratings

TOG stands for Thermal Overall Grade — it's a measure of how much warmth a fabric provides. For baby sleeping bags, the correct TOG depends on the temperature of your baby's room:

• 0.5 TOG: Suitable for rooms above 24°C — very warm summer nights.
• 1.0 TOG: Suitable for rooms between 20–24°C — typical UK room temperature.
• 2.5 TOG: Suitable for rooms between 16–20°C — cooler rooms or winter months.
• 3.5 TOG: Suitable for rooms below 16°C — very cold conditions, less commonly needed with central heating.

The recommended room temperature for a sleeping baby is 16–20°C. A room thermometer in the nursery is a worthwhile investment that takes all the guesswork out of TOG selection.

What Makes a Good Baby Sleeping Bag?

Not all sleeping bags are equal. Here's what to look for:

• Correctly sized neck opening: The neck hole should be snug enough that the baby cannot slip down into the bag. Check sizing guides carefully — bags that are too large are a safety risk.
• Shoulder fastenings or zip from the bottom: A bottom-opening zip makes nappy changes easier at night without fully removing the bag and disturbing sleep.
• Breathable, natural fabric: Organic cotton is the gold standard. It regulates temperature better than synthetic materials and is gentler on sensitive skin.
• No hood: Sleeping bags should never have a hood — hoods can cover a baby's face during sleep.
• Correct TOG for the season: Have two different TOG ratings on hand — one for summer, one for winter.

Can You Ever Use a Blanket?

If you do use a blanket — for example, during supervised naps or in a pram — there are ways to reduce risk. The blanket should be tucked firmly under the mattress on three sides, reaching no higher than the baby's shoulders. Cellular cotton blankets (those with a woven hole pattern) are preferable to thick fleece because they allow more airflow even if they shift upward.

For unsupervised sleep, particularly overnight, a properly fitted sleeping bag remains the safest choice for babies under 12 months.

When to Switch to a Blanket

Most parents transition away from sleeping bags at around 18 months to 2 years, when toddlers start to move around more during sleep and may want to pull a blanket themselves. At this age, the risks associated with loose bedding are significantly reduced because the child has sufficient motor control to manage the bedding.

Frequently Asked Questions