Can my baby sleep on a second-hand mattress?
Guidance differs by country — If reused: 100% waterproof cover, no rips or tears, firm and flat, and a snug fit within 20mm of the cot sides
This is a genuine national disagreement. The Lullaby Trust advises buying a new mattress for each baby, because research suggests one from outside the family home increases SIDS risk. Red Nose Australia says there is no evidence of increased risk provided the mattress is firm, flat, clean and well fitting.
The verdict
Two national safer sleep charities have looked at this question and reached different answers, and they are both current.
The Lullaby Trust advises buying a new mattress for each baby, on the basis that research suggests using a second-hand mattress from outside the family home increases the risk of SIDS. Red Nose Australia states that there is no evidence to show an increased risk of SIDS for babies who sleep on a second-hand mattress, providing a list of conditions is met.
That is an unusually clean disagreement, and it is worth understanding rather than picking a side at random.
Where the UK position comes from
The Lullaby Trust's caution is specific in a way that is easy to miss: it is about a mattress from outside the family home. A mattress passed down from an older sibling within the same household is treated differently from one bought at a car boot sale or given by a friend.
The underlying research examined whether reused infant mattresses were associated with SIDS and found a signal, with the association strongest for mattresses that came from another household. Nobody has established a mechanism, and the leading hypotheses – residual microbial contamination, degradation of the surface, loss of firmness with age – are hypotheses.
The Lullaby Trust's response is precautionary. It recommends new where possible, and then, recognising that new is not always possible, tells you what an acceptable second-hand mattress looks like.
Where the Australian position comes from
Red Nose approaches the same evidence and concludes that the mattress's history is not the variable that matters. What matters is its condition and how it is used.
Its conditions are worth quoting in full, because they are the most detailed published specification for a cot mattress anywhere:
Baby is placed on their back to sleep. Baby sleeps on a firm mattress that is flat, not tilted or elevated in any way. The mattress is clean and in good condition. The mattress fits snugly, within 20 mm of the sides and ends of the cot – check that you cannot fit more than two fingers between the mattress and the cot sides. Baby sleeps with no bedding covering their face or head. And there are no loose items such as pillows, blankets, toys or bumpers in the cot.
The two-finger test
That gap test is the single most useful thing on this page, and it applies whether your mattress is new or not. A gap wider than two fingers between the mattress and the cot side is a wedging hazard: a baby who rolls into it can become trapped with their face against the mattress or the cot frame.
A second-hand mattress that came out of a different cot is more likely to fail this test than a new one bought for the cot you own, which is a real, practical argument for buying new that has nothing to do with the SIDS association.
What both bodies want, whichever line you take
Strip out the disagreement and the shared checklist is substantial.
Firm. Press it. Your hand should not sink in. A mattress that has developed a body-shaped dip has failed regardless of its age.
Flat. Never tilted, propped, wedged or inclined. The Lullaby Trust says not to incline, tilt or prop the mattress, cot or baby, because it does not help with reflux.
Waterproof and intact. The Lullaby Trust asks for a well fitting, 100% waterproof cover and no rips or tears. A tear lets fluid into the foam, and a wet foam core is the thing you cannot clean.
Clean and in good condition. Red Nose's phrasing. Staining, smell, visible mould or damp all disqualify it.
A snug fit. Within 20 mm all round, two fingers maximum.
Nothing on top of it. A fitted sheet and nothing else. No mattress topper, no quilted protector, no folded towel, no sheepskin. The AAP names mattress toppers and non-fitted sheets on its exclusion list.
The wider second-hand checklist
The Lullaby Trust's advice on second-hand baby products generally is worth applying to the cot as well as the mattress, and it is sensible.
Make sure you can get hold of the product's instructions – you can usually download them from the manufacturer's website. Make sure the product meets the relevant British safety standards, stated on the product, its packaging or the manufacturer's website. Search online to check the product has not been recalled or deemed unsafe; you can search "product recalls" on GOV.UK. Make sure it is in good condition with no broken or missing parts.
And a point that applies particularly to soft goods: any second-hand items should come from a smoke-free and pet-free home.
The Lullaby Trust also suggests taking a phone with you when shopping second-hand, so you can look a product up before you buy rather than after.
Where second-hand is a poor idea regardless
Nothing here contradicts the separate, much firmer advice about second-hand car seats, where an invisible crash history can compromise a shell. A mattress has no equivalent hidden failure mode, which is one reason the two questions get different answers.
So which line should you take?
The honest answer is that both are defensible and the practical gap between them is smaller than it looks.
If you can buy new, buy new. It resolves the UK caution, guarantees the fit to your cot, and costs less than most nursery furniture. If you cannot, a firm, flat, clean, undamaged mattress with an intact waterproof cover that fits your cot within two fingers all round is what both bodies describe as acceptable – Red Nose calls it safe, and the Lullaby Trust calls it the version to use if new is not possible.
What neither of them accepts is a soft, sagging, torn or ill-fitting mattress, and that is the failure mode that actually shows up in second-hand equipment.
Where guidance genuinely differs
New versus conditional. The Lullaby Trust generally advises new for each baby. Red Nose says there is no evidence of increased risk if the conditions are met. Same question, different conclusions, both published today.
Only the UK distinguishes inside from outside the household. The research the Lullaby Trust cites points at mattresses from another home. A hand-me-down from an older sibling in the same house is not the case the caution is built on.
Only Australia gives a measurable fit tolerance. 20 mm, or two fingers. That is the one number on this page you can act on tonight, whichever mattress you own.
The United States does not engage with provenance at all. American guidance is entirely about firmness, flatness, fit and nothing on top – which means a second-hand mattress in good condition meets it without further argument.
The Lullaby Trust generally advises buying a new mattress for each baby, because research suggests using a second-hand mattress from outside the family home increases the risk of sudden infant death syndrome. It accepts that this is not always possible, and sets criteria for one that is reused: it should have a well fitting, 100% waterproof cover, no rips or tears, and be firm and flat. Its wider second-hand checklist asks you to make sure you can get hold of the product's instructions, that the product meets the relevant British safety standards, that it has not been recalled – you can search "product recalls" on GOV.UK – and that it is in good condition with no broken or missing parts. Any second-hand items should come from a smoke-free and pet-free home.
Showing guidance from The Lullaby Trust — read the source.
Red Nose Australia reaches the opposite conclusion from the same question. It states that there is no evidence to show an increased risk of SIDS for babies who sleep on a second-hand mattress, providing that: baby is placed on their back to sleep; baby sleeps on a firm mattress that is flat, not tilted or elevated in any way; the mattress is clean and in good condition; the mattress fits snugly, within 20 mm of the sides and ends of the cot – check that you cannot fit more than two fingers between the mattress and the cot sides; baby sleeps with no bedding covering their face or head; and there are no loose items such as pillows, blankets, toys or bumpers in the cot. Babies should sleep on a firm, clean, well-fitting mattress that is in good condition.
Showing guidance from Red Nose Australia — read the source.
American guidance does not address mattress provenance and concentrates entirely on firmness and fit. The American Academy of Pediatrics asks for a firm, flat, non-inclined sleep surface with a fitted sheet and nothing else, and rules out mattress toppers, non-fitted sheets, quilts, comforters, pillows and pillow-like toys. A second-hand mattress that is firm, flat, undamaged and fits the cot with a fitted sheet meets American guidance; one that has softened, sagged or been topped does not.
Showing guidance from American Academy of Pediatrics — read the source.
Sources
- Second-hand baby products — The Lullaby Trust, accessed
- Is it safe to use a second-hand mattress? — Red Nose Australia, accessed
- What is a safe mattress? — Red Nose Australia, accessed
- Sudden infant death syndrome (SIDS) — NHS, accessed
- Keeping a clear cot: the safest cot — The Lullaby Trust, accessed
- How to Keep Your Sleeping Baby Safe: AAP Policy Explained — American Academy of Pediatrics (HealthyChildren.org), accessed