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18 Mar 2021

Five mistakes to avoid when buying your cot mattress

From avoiding outlandish claims to not overspending, we tell you what to look out for to get the best cot mattress for your baby
baby in cot crying

It's important that your child has a cot mattress that's flat, supportive and safe so you both get a peaceful night's sleep.

After all, you don't want to end up spending more money than you need to on a cot mattress that isn't up to standard.

Based on our extensive lab testing and expert advice, we've highlighted five mistakes you can avoid when buying your next cot mattress, saving you money, time and stress.

Best Buy cot mattresses - see which ones have aced our safety tests

1. Going for the most expensive cot mattress

It makes sense to think that the more expensive a cot mattress is, the better it will be for your baby.

But our many years of testing cot mattresses for support, safety and durability shows that to not be the case.

Below, is a graph of all our tested cot mattresses as of March 2021, comparing their price with their Which? test score.

graph showing no correlation between cot mattress

As you can see, the points are all over the place, meaning there's no clear trend between the price of a mattress and how it's performed in our tests.

Comparing just our Best Buy cot mattresses to our Don't Buys, we find an average price of £93 for a Best Buy and £132 for a Don't Buy. Further proof that the quality of a cot mattress doesn't always go up with price.

So don't just go for a cot mattress because of the cost, instead use our reviews and the other tips below to help you narrow down your search.

Cot mattress reviews - find the perfect cot mattress at the price you want

parent inspecting cot mattress

2. Assuming all cot mattresses provide enough support

NHS guidance says that cot mattresses need to be firm, flat and fit the cot snugly without leaving gaps around the edges to ensure your baby sleeps safely and their growing bones are provided with vital support.

It's reasonable to think that every cot mattress you can buy will meet the needs of your growing child.

However, our safety testing has unfortunately revealed cot mattresses that not only provide little support, but some are too soft and pose a potential suffocation risk to young babies.

Some 44% of cot mattresses that we've tested as of March 2021 have been Don't Buys. So while there are some great ones out there, it's worth doing your research to make sure you're buying the best.

How Which? safety tests cot mattresses

We test cot mattresses to the BS EN 16890:2017 safety standard. This means check we check for:

  • Suffocation risks Both on the mattress as new and after the durability test
  • Choking and hazard riskssuch as loose zips and stickers
  • Entrapment risks Checking the dimensions of the cot mattress are accurate and will fit in the correctly sized cot bed without spaces around the edges.

This standard is voluntary, meaning that it's not a requirement manufacturers meet it. However, we test to this standard because we believe it goes further to ensure a safe sleeping environment for babies and young children.

hand testing firmness of cot mattress

How to tell if a cot mattress is firm enough

The first port of call is to read our reviews to find the models our testing found to be firm and supportive.

If you want to assess the cot mattress yourself use these simple checks to make sure its firm:

  1. Look to see if the mattress sits flat when in your baby's cot or cot bed
  2. Press your hand firmly into the centre of the mattress - there should be resistance and it should bounce back immediately after you remove your hand
  3. Repeat this at the edges of the cot mattress - again, there should be resistance and it should bounce back immediately.

Finally, don't worry if a cot mattress feels too firm for you - a baby's mattress needs to be firmer than an adult mattress in order to provide vital support as they grow.

Cot mattress safety - more tips on getting the best cot mattress

hand putting a cover on a cot mattress

3. Going for a breathable mattress instead of a waterproof one

The Lullaby Trust suggests a waterproof mattress is more important than a breathable one.

This is because having a waterproof cover on your baby's cot mattress helps to stop bacteria building up inside the mattress, reducing the risk of illness. A baby's temperature can be regulated through other means, so a breathable mattress is less important.

At Which?, we check to see how a mattress copes with inevitable leaks and accidents. We also test the washability of the cover to see whether it shrinks after several washes.

If a cover shrinks, then it could compress the size of the mattress - the smaller dimensions might mean gaps appear between the cot mattress and the cot bed frame, presenting a risk of your baby trapping a limb and becoming stuck.

However, if a breathable mattress is a top priority for you, we also test this using special equipment to check the airflow through the mattress.

room thermometer

Regulating your babies temperature

There are ways to regulate your baby's temperature without bringing the cot mattress into it. Here are some top tips suggested by the NHS and Lullaby Trust:

  • Use a light blanket or baby sleeping bag for warmth Make sure it's tucked in firmly and below your baby's shoulder level. Read our baby sleeping bags investigation to see the results of our snapshot test.
  • Don't use pillows or duvets They're not safe for babies under the age of one. They could be a suffocation risk and a duvet could overheat them.
  • Use a room thermometer to stop it getting too hot or cold Anything between 16°C to 20°C is ideal for the room your baby sleeps in.

How we test cot mattresses - learn about the extensive lab testing we do to check cot mattresses are safe.

pile of assorted baby products

4. Pimping out your baby's cot with accessories

There are a huge range of baby products out there, so it can be confusing to know what you need to get and sometimes it can feel like you need everything.

Luckily, the advice from the Lullaby Trust is clear, and it will save you money and stress: the safest cot is a clear cot.

There is some evidence of a higher risk of Sudden Infant Death Syndrome (SIDS) if babies have their head covered, and some items that can be added to a cot increase the risk of covering your child's head or face.

Here are some of the items you don't really need for a cot:

  • Soft toys If a baby ends up face down in a soft toy it could pose a suffocation risk. Keep the cot clear and let them play with their favourite toy when awake.
  • Sleep positioners They don't provide a flat surface for your baby to sleep on. Remember, it needs to be firm and flat in case your baby rolls unexpectedly.
  • Cot bumpers The Lullaby Trust says they can pose a serious hazard to babies due to the risk of becoming entangled in the ties or material.

amazed parents looking at a laptop

5. Going for a cot mattress with a fancy claim

Some cot mattresses come with claims that sound too good to be true - and they often are.

Manufacturers want their product to stand out from the crowd, but all expert advice - and our testing - point to three simple things to check for: is it firm, flat and waterproof? If it does these well, it will be safe and supportive for your baby.

Here are some claims we've come across during our testing, and some the Lullaby Trust says its best to ignore:

'Eliminates allergens'

This may seem semantic, but claims to eliminate allergens - instead of being anti-allergen or hypoallergenic - are misleading and can give a false sense of what the mattress can do.

Bed Advice UK states: 'For a mattress, hypoallergenic means it's allegedly safe for people suffering with allergies - although it's not a guarantee. The mattresses will reduce allergies by preventing dust mites from penetrating the surface and bedding in.'

'Reduces risk of SIDS'

While the safety standard we test to goes further than the mandatory standards, none can specifically assess whether a product decreases or increases the risk of SIDS.

Claims that a product will decrease the risk of SIDS are almost always not true. However, products that conform to safe sleep advice will be less risky than those that don't.

And, remember, a firm, flat and waterproof mattress will be the safest one for your baby.

'Reduces the risk of flat-head syndrome (Plagiocephaly)'

We all want to protect our baby. As their heads are softer, they can become naturally flattened and it can be a source of worry for some parents.

However, a product should not be needed to prevent or reduce this. If a mattress claims to be soft enough to reduce flat-head syndrome, then it's more than likely not firm enough to properly support your baby, which could pose a suffocation risk.

The Lullaby Trust recommends plenty of supervised 'tummy time' when your baby is awake and to speak to your doctor or health advisor if you're worried.

For even more advice on recommended products for safer sleeping, see the Lullaby Trusts Product Guide.

Which cot mattress should you buy - read our expert advice on how to buy the best