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Cot mattresses

By Lisa Galliers

Give your little one the best and safest sleeping space with our top cot mattress tips.

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Cot mattress safety

A crucial part of baby cot safety is choosing the best cot mattress. Here are our tips to make sure your cot mattress measures up. 

  • Make sure you choose the right size of mattress.
  • Make sure the mattress is firm and flat, and protected by a waterproof cover
  • Avoid second-hand mattresses where possible.
  • Check any mattress you use conforms to current safety requirements. 
  • Mattresses should carry the BSI number BS 1877-10:2011+A1:2012.
  • The mattress should fit the cot with no gaps down the side that are more than 4cm.

The Lullaby Trust recommends you buy a new cot mattress for your baby, where possible. 

If you have a second-hand mattress, whether it's a mattress you've used for one of your other children or one that has been given to you, check the following:

  • That the mattress is in good condition; that it's flat, firm, not soft, fits the cot without any gaps and doesn't sag.
  • It has been cleaned and dried thoroughly.
  • Check that it was previously used with a waterproof cover.
  • Make sure you use it with a waterproof cover.
  • Check it's free from cracks or tears or holes.

Find the best cot bed to use with your cot mattress in our cot bed reviews

Choosing a cot mattress

Check the cot mattress size

A mattress around 8-10cm thick is enough to support your baby.

Mattresses come in two basic sizes to fit the equivalent sizes of cot generally available in the shops. 

Your cot will specify which type of cot mattress it requires: standard (56x118cm) or continental (60x120cm). If the mattress is the wrong size, your baby could be dangerously trapped in gaps between the cot and the mattress. 

The gap between the mattress and the cot should be no more than 4cm (1.5 in)

If you buy a cot that is smaller or larger than the norm, you can get mattresses specially made to fit your cot.

Choose one that's easy to keep clean

To keep the mattress as hygienic and clean as possible, choose one with a PVC-covering or a removable top panel that you can wash at a reasonably high temperature.

Squeeze for firmness and measure for thickness

Squeeze a selection of mattresses in the shop and choose one that feels firm rather than soft. 

To compare firmness, squeeze at the edges and at the centre. Your baby needs a mattress that provides good support and won't sag.

Look for a cot mattress that is around 10cm thick. Anything thinner won't provide the support your baby needs. Thin foam, in particular, can lose its shape and dent easily.

A travel cot mattress should be no more than 10cm thick and you should expect the mattress in a crib or Moses basket to be no more than 5cm thick. These thicknesses are specified in BS 1877:Part 10:1997, the safety regulations that govern cot mattresses.

Check out our Best Buy cot beds.

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Types of cot mattresses

Foam mattresses

Foam mattresses tend to be the least expensive. The simplest versions are made from a single layer of supportive foam completely covered with a wipe-clean, waterproof PVC cover. Some foam mattresses have ventilation holes, but these aren't necessary.


  • Generally easy to keep clean.
  • Good value for money.
  • Can provide good support and resistance to denting.


  • Some parents may not like the idea of the basic PVC-covered mattress because of concerns about clamminess.
  • Mattresses with ventilation holes (designed to help keep your baby cool) can be more effort to keep clean if your baby is a dribbler or is often sick, because residue can gather in the holes and mesh.

Safe sleeping tipsessential bedtime know-how for parents.

Spring-interior cot mattresses

These traditional mattresses have a coiled spring interior with layers of felt and foam padding. They often have a cotton cover on one side and PVC or other wipe-clean material on the other.


  • Many parents like the familiarity of a traditional spring mattress.
  • The wipe-clean side is the recommended surface for your baby to sleep on because of the practical advantages, but you can flip it over onto the cotton side if you prefer – eg, if it's hot and your baby feels clammy.


  • More expensive than foam mattresses.
  • The cotton side may be preferred for comfort but can be more difficult to keep clean (unless you buy a mattress with a removable panel).

Coir or natural fibre cot mattresses

These have a core of coconut fibre with other layers of different materials. The fibres are coated in latex for strength and protection, and the natural fibre filling helps air to circulate through the mattress. These mattresses are available with a wipe-clean covering.


  • One of the firmest types of mattress.
  • Tend to last longer because they hold their shape well, so could be a sensible purchase if you want to use it for more than one child.


  • Less widely available than foam or spring interior.
  • Can be more expensive than the alternatives.

Hypoallergenic cot mattress

These have a quilted top layer that can be easily detached from the body of the mattress, so you can wash it at 60°C to kill any dust mites that may cause allergies.

Allergy UK has a list of approved mattress covers and bedding on its website.


  • Easy to keep clean


  • May be more expensive than other kinds of mattress

Using cot beds safely – now you've got your mattress sorted, check out these safety essentials.

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