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28 Jan 2020

Why are so many cot mattresses failing safety tests?

We've found safety issues in more than 60% of cot mattresses we've tested recently. Find out what they are, and how you can ensure a secure night's sleep for your baby

Which? has tested 26 cot mattresses from big brands between 2018 to 2020. We've named 15 of these cot mattresses Don't Buys because they failed key safety tests that make up part of the 2017 British Safety Standard.

We're concerned by this high failure rate, and want parents and carers to be vigilant at spotting these potential issues with their own cot mattresses.

Read on to find out what we discovered in our tests, and how you can ensure a suitable and safe sleeping environment for your little one.

Best Buy cot mattresses - read reviews of the impressive cot mattresses that passed our stringent tests.

Safety tests that cot mattresses are failing

Our safety tests replicate those in the current cot mattress safety standard, which is called BS EN 16890:2017.

Approved in September 2017, it's a voluntary standard, which means it's not a requirement. However, manufacturers are strongly encouraged to meet these standards to minimise risks and hazards for babies and young children.

The four key safety tests we've seen cot mattresses repeatedly fail are:

Lack of firmness

A cot mattress is automatically downgraded to a 0% Don't Buy if our tests highlight a serious safety risk.

If the top layers of the mattress are too soft and your baby accidentally rolls on to their front, their face could sink into the mattress. This poses a suffocation risk.

It's a concern with babies aged between four and 12 weeks, when they are commonly able to roll over from their back to their front.

Rolling from front to back requires more strength, and in some cases a baby may not master this skill until they reach around six months old.

Both the Stokke Home Bed Mattress and Babydunlopillo Safer Sleep Cot Bed Mattress failed the firmness test when new, so we recommend that you avoid these mattresses if your baby is less than six months old, to mitigate this risk.

Stokke told us it has updated this mattress and the old product is no longer in circulation, but we haven't verified this with our testing, and the two products share the same name.

Baby Dunlopillo told us its mattress complies with all applicable mandatory safety standards. It did, however, remove the product from sale pending its own internal investigations.

Find the brands recommended by parents in our guide to the best cot mattresses

Choking hazards

Ideally, you want to invest in a cot mattress with a removable and washable cover to help keep your baby's mattress clean. Many cot mattresses have a zip to help you remove the cover from the mattress easily.

But our tests identified cot mattresses with accessible zip pulls that can detach easily and become a choking risk or swallowing hazard.

This is an unnecessary risk which could be mitigated by having a small pocket for the zip pull, to ensure that little hands can't reach it in the middle of the night.

Three out of the five cot mattresses we tested in December 2019 had zip pulls that came off in our tests, and one even had a sharp spike to lock the zip pull in place, which could cause injury.

If your child's cot mattress has a zip pull that's easy to get to, we'd advise sticking a piece of strong tape, such as duct tape or gaffer tape, over the top and using a tightly fitted sheet on to further restrict access to the zip pull.

Cover shrinkage

While cover shrinkage may not immediately seem serious, a shrunken cover can compress the cot mattress and reduce its size.

The smaller dimensions might mean that the mattress no longer sits flush within the cot bed. If there's a gap of a few centimetres, there's a risk that a baby could trap a limb and become stuck.

If your baby becomes trapped and is positioned face down, it could be a serious suffocation risk.

Incorrect dimensions

As we've mentioned, the size of your cot mattress is very important. There shouldn't be any gaps between the mattress and the cot or bed that are more than 3cm. The mattress should also be firm and very flat.

Manufacturers should be making cot mattresses that are 140 x 70cm or 120 x 60cm, which are the standard sizes for cot and cot bed mattresses.

But there's clearly a quality-control issue, as some cot mattresses we've tested are either too small (potentially causing an unsafe gap) or too large (which means they don't sit flat).

We've also seen incorrect information and wrong advice on cot mattress labels, and instructions that could compromise a baby's safety.

Read our cot mattress safety guide to find more tips and advice about using your cot mattress safely.


Stickers may seem innocuous, but there are two reasons why manufacturers shouldn't be putting them on cot mattresses.

Firstly, a sticker is a potential suffocation hazard and a choking risk if your little one decides to play with it and put it in their mouth.

Secondly, these stickers typically include important information, such which side is suitable for sleeping, or the age restrictions for each side, which should be permanently attached to the mattress to help parents and carers to use it safely.

For example, the Silver Cross Superior Cot Mattress (pictured below) is permanently labelled with a 'baby side' for little ones under 18 months and a 'toddler side' for children of more than 18 months.

If you buy a cot mattress that has a sticker on it, make sure you remove it before use and note down the information either on the label, or somewhere safe so you can refer to it if need be.