Foam, Sprung or Natural: Which Cot Mattress Type Is Best?

Every cot mattress sold in the UK should meet the same two standards regardless of what is inside it: BS EN 16890:2017+A1:2021, the safety standard for cot and crib mattresses, which covers firmness and entrapment testing, and BS 7177:2008+A1:2011 for resistance to ignition, which is the fire-resistant label on the side. Both appear on The Lullaby Trust's own list of standards to look for.

On top of the standards sit the three Lullaby Trust questions: is it firm, is it flat, does it have a waterproof cover? Their firmness test works on any filling: when your baby lies on the mattress, their head should sink in no more than a few millimetres. Their reasoning is blunt: soft mattresses are known to increase the risk of sudden infant death syndrome.

And before any of this, the size. A mattress of any type that leaves a gap at the edge fails before the filling gets a vote; the cot standard allows at most 3 cm between mattress and frame. Look your cot up for the exact size, or see our sizes guide.

The entry level is a block of polyurethane foam or bonded polyester fibre in a wipeable or removable cover, and as we write this the going rate for a 140 x 70 cm cot bed size is roughly £25 to £65. Mother Nurture's Classic Eco Fibre sells for around £39 and its dual-sided Slumberpad Plus for around £63, to pick the brand we know best.

The honest case for foam: it is light, which matters more than it sounds when you are stripping a cot one-handed at 3am; it holds no springs to loosen; and a decent one passes every safety test that matters. For a standard cot that will be outgrown around age two, a good foam mattress is a perfectly rational choice, and the money saved buys a lot of fitted sheets.

The honest case against: foam fatigues. Under a child who starts at 3 kg and leaves at 15 kg plus, with four years of toddler bouncing at the end, a budget core can soften and dip before a cot bed's term is up. If you go foam on a cot bed, check it against the firmness test every few months and treat a sag as the end; our replacement guide covers the signs.

Spring cores borrow adult mattress engineering, in two tiers:

• Open coil is a single lattice of springs with foam or fibre padding above, typically £60 to £90; Mother Nurture's Classic Spring runs around £73 and Mamas & Papas' sprung cot bed mattress around £72. It is the durability-per-pound sweet spot: a spring core resists the slow sag that kills foam.
• Pocket sprung puts each spring in its own fabric pocket so it compresses independently, typically £80 to £200 depending on brand ambition. Mother Nurture's is around £81; Mamas & Papas run £115 to £149; Silver Cross's TrueFit sells around £125. Makers pitch independent support and quieter movement, and several build dual-sided designs with a firmer infant side and a softer toddler side you flip to later.

Our view: springs earn their money on a cot bed, where the mattress has to stay firm and flat from newborn to roughly age four. On a standard cot with a two-year service life, the case is weaker and a good foam mattress closes most of the gap. One caution on dual-sided designs: the sides are not interchangeable. The infant side is the firm side, and it is the only side a baby should sleep on; flip only when the maker says the child is old enough.

The premium tier swaps synthetics for natural materials: coconut coir cores, organic lambswool padding, natural latex, organic cotton covers. Naturalmat, the best-known UK maker, sells its coir Coco Mat at £250 in cot bed size and its Latex Mat at £280, and the broader bracket runs roughly £150 to £300. The claims are about materials rather than performance: Naturalmat's copy is "completely chemical free", with Soil Association certified wool, a cover it describes as naturally fireproof without synthetic fire-retardant treatment, and a plant-based dust mite treatment.

Be clear-eyed about what the premium buys. These are genuinely lovely, durable, hand-made things, and if avoiding synthetic materials or fire-retardant chemicals matters to you, this is the tier that delivers it. What it does not buy is extra safety: a natural mattress answers the same three Lullaby Trust questions as a £39 foam one, no more. The safety bodies do not rank fillings.

If you go natural, apply the same rules as everyone else: exact size for your cot, a waterproof layer over it from day one (wool is absorbent, and a £250 core is the last thing you want a leak reaching), and the firmness test on arrival, because handmade softness varies.

The Lullaby Trust's product guide has a section literally titled "Claims you should ignore", and cot mattresses are where those claims live:

• "Breathable". Their words: "Rather than being breathable it is more important that the mattress is waterproof, or has a fitted waterproof cover or layer." The best way to keep a baby at safe temperature is a firm, flat surface, on their back, in a 16 to 20 degree room, not a clever fabric.
• "Reduces the risk of SIDS". Their words again: "Claims that a product will decrease the risk of SIDS are almost always not true." No mattress standard tests for SIDS risk; the standards cover construction, chemicals and fire.
• Ventilation holes. No official body asks for them or validates them. Harmless, but a feature, not a safety credential, and never a reason to pay more.
• Memory foam and "contouring comfort". The Lullaby Trust does not name memory foam, so we will not pretend they do. But their firmness rule does the work: a surface a baby's head sinks into beyond a few millimetres fails, and moulding to the sleeper is memory foam's entire sales pitch. A surface that cradles an adult shoulder is the wrong surface for a baby. Keep conforming foams for your own bed until the toddler years are done.

Buy by how long the mattress has to serve, then by budget:

• Standard cot, roughly two years of service: a quality foam or fibre mattress with a proper waterproof cover. Spend £40 to £65, not £150.
• Cot bed, birth to around four: this is where springs pay for themselves. An open coil around £70 to £90 is the value pick; pocket sprung with a dual-sided design is the comfort upgrade if the budget stretches.
• Natural fibre: choose it because the materials matter to you, with eyes open that the safety is equal, not superior. It is the one tier where the protector is non-negotiable from night one.

Whatever the filling, the sequence does not change: exact size first, firm flat and waterproof second, type last. Start with your cot and the size takes ten seconds.