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Find out why your second-hand cot mattress could be unsafe

Which? survey finds 9 in 10 parents have issues with their second-hand cot mattress

Find out why your second-hand cot mattress could be unsafe

What parents want from their baby’s cot mattress is proper support and safety.

However, our recent survey of 1,878 parents with a child under the age of five found almost nine in 10 experience issues with their second-hand cot mattress.

This is dramatically higher than those who’d bought the cot mattress new, where around five in 10 said they experienced issues.

While some of the problems identified may not seem like a deal breaker, they could lead to bigger safety problems – and put your child at risk – in the future.

Find out what parents told us about their cot mattresses, and the issues to look out for.


Best Buy cot mattresses – find a new cot mattress that will safely support your child for years to come


dad holding and inspecting cot mattress

Second-hand cot mattresses issues

In February 2021, we asked parents to identify issues they’d had with their current cot mattress, and to tell us if that mattress was bought new or if it was second-hand.

In the graph below we’ve broken down the type of issue along with the percentage of new and second-hand cot mattress owners with that issue.

bar chart showing issues with cot mattresses new vs. second-hand

See our Cot mattress safety guide for all the results

As you can see, it doesn’t matter what the problem is, parents with a second-hand cot mattress are about twice as likely to have one.

While some of these issues would be annoying on an adult mattress, they can lead to potential safety risks for your growing baby.

  • Gap(s) between the mattress and bed frame – This could lead to a baby getting their arm or leg trapped, potentially leading to a physical injury.
  • Mattress sagging too much – A cot mattress that isn’t firm doesn’t provide enough support for your growing child and could be a suffocation risk if your baby ends up on their front, face-down on the mattress.
  • Zips on covers breaking – A zip is usually small enough to present a choking hazard to babies.

Cot mattress buying guide – discover the top-rated brands from our tests and by parents


mum and baby looking at laptop screen

Is it safe to use a second-hand cot mattress?

Which? do not recommend parents buy a cot mattress second-hand.

This is also the view of The Lullaby Trust, as there is research that found an increased chance of Sudden Infant Death Syndrome (SIDS) when using a second-hand mattress brought in from outside of the family home, although the link is not yet proven.

We test cot mattresses to the BS EN 16890:2017 cot mattress standard. This means we check that a cot mattress provides enough support, is durable enough, and is safe for your child.

Only cot mattresses that meet all these criteria can be a Best Buy.


Find out what goes into finding the best cot mattresses by reading our How we test guide


If you need to buy second-hand, the risk can be reduced by making sure you know the history of the mattress and by checking it yourself before purchasing.

Use our checklist below to make sure a second-hand cot mattress (whether bought or a hand-me-down) will be safe for your baby:

    1. Test to see if it’s still firm and lies flat, with no holes or tears – when you press down there should be resistance and the mattress should spring back immediately when you remove it.
    2. Check the mattress isn’t sagging in places – that part of the cot mattress won’t provide enough support for your child, and could be a suffocation risk.
    3. Make sure the cot mattress was previously protected by a waterproof cover – this will reduce the risk of unhealthy bacteria lurking in the materials.
    4. Make sure it fits the cot bed with no gaps around the edges – take a tape measure and check the length and width of the mattress at multiple places on the mattress. The standard size mattress for a UK cot bed is 140cm x 70cm, but double check the cot mattress size your cot bed needs beforehand.

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