Foam and compressed polyester fibre are both used in baby mattresses. Fibre is often chosen for budget models, but price alone does not tell you how well a mattress will retain its shape and support as your baby grows.

So, what is the difference, and what should you look for when choosing a mattress?

Understanding a fibre core

A basic polyester-fibre mattress has a core made from fibres compressed together to form a pad. Its feel and performance depend on how that pad is made and how much material it contains.

A firm feel when new does not, on its own, tell you how well a mattress will withstand repeated use. Ask how the finished mattress has been tested and whether the manufacturer provides information about its durability. It is too broad to say that every fibre mattress will flatten or need replacing after a set period.

Why quality foam performs differently

Flexible foam has a cellular structure that compresses under pressure and recovers when the pressure is removed. The grade selected affects its firmness, resilience and durability.

Density and firmness are separate measurements. Density can help indicate likely durability when comparing similar foams, while firmness describes resistance to compression under specified test conditions. Neither figure, by itself, proves that a finished mattress is suitable for a baby.

Not all foam is the same. A description such as “high density” is more useful when the manufacturer also publishes the actual specification.

For example, the foam surrounding the pocket springs in our Gold Sprung mattress is grade 35/135: its specified density is 35 kg/m³ and its firmness rating is 135 newtons. You can read more in our guide to understanding foam quality.

What about breathability

Airflow depends on the construction of the whole mattress, including its core, cover and protective layers. The material name alone does not establish how breathable the finished mattress will be.

Gold Sprung combines individually pocketed springs with foam on the top, bottom and sides. Its removable honeycomb cover has a spacer-fabric backing. These construction details give parents a clearer picture of what is inside the mattress than a general marketing label.

For safer sleep, keep the essentials in view: The Lullaby Trust recommends a firm, flat mattress with a waterproof cover. A claim about breathability does not replace those requirements.

Looking beyond the price

A cot-bed mattress may be used through several stages of your child’s early years, within the cot or bed manufacturer’s age and size limits. Before buying, ask:

  • What materials form the core, and how is the mattress constructed?
  • Does it have a waterproof cover or layer, and what area does that protection cover?
  • How has the finished mattress been tested for firmness and durability?
  • Does the manufacturer publish the foam density or other performance specifications?
  • What care does it need, and what does the guarantee cover?

“Water resistant” and “waterproof” are different claims, so check the details. Follow the care instructions and check regularly for damage, sagging or a lasting indentation.

Making sense of marketing terms

Words such as “eco”, “orthopaedic”, “premium” and “hypoallergenic” do not tell you how long a mattress will last or how well its core will retain its shape.

If a mattress is described as “eco”, ask what supports that description. Does it contain recycled material? Can it be recycled through an available collection scheme? Is there evidence for a claimed reduction in environmental impact?

Likewise, an allergy-related claim is not a measurement of firmness or durability. Look for a clear explanation and supporting evidence.

Our conclusion

We value carefully specified foam for its measurable properties and recovery after compression. But choosing well means looking at the complete mattress, its testing, fit, care requirements and condition, rather than assuming that one material or a higher price guarantees quality.

Choose a mattress that provides a firm, flat sleeping surface, fits your cot or cot bed correctly and can be kept clean and dry. Good value comes from a mattress that continues to do its job.