How to Choose a Safe Cot Mattress

Buying a cot and mattress is one of the biggest purchases you’ll make when setting up your baby’s nursery. It’s also one of the most frequently used items with babies sleeping for most of the day when younger and often remaining in their cot until around 3 years of age.  

However, it’s not just cost and longevity you need to keep in mind when choosing a cot mattress, but also the firmness and safety of the mattress. Whilst there are safety standards for household cots in New Zealand and Australia (AS/NZS 2172:2003 Cots for household use) and travel cots, there are no such mandatory safety standard for cot mattresses. Unfortunately you can't assume that cot (and bassinet or moses baskets) for sale in New Zealand are safe to use with newborns.

So we recommend that you do your research before you buy your baby’s mattress. You can check if mattresses have been checked with the standard test to measure the firmness of a mattress (AS/NZS 8811.1:2013 Method 1: Sleep Surfaces – Test for firmness). This will tell you firstly that the supplier takes mattress safety seriously and also that it is safe to use with your baby. Overseas mattresses, such as European brands, may comply with a different safety standard.

Firmness Testing for Cot Mattresses

Most parents will be aware that baby’s first cot mattresses need to be firm, but how firm is firm? And why does it need to be so firm when as adults many of us like softer mattresses?

Previous studies have linked overly soft infant mattresses with suffocation and it’s easy to see why when you look at the test results below for a soft mattress. A firm mattress will properly support a baby during their sleep and means that if they roll over during their sleep, their nose won’t become cushioned in the mattress, potentially obstructing their breathing.

Once you’re happy with the firmness of your chosen mattress, you should take care not to soften it by adding toppers or sheepskins. We recommended wool underlays for babies older than 6 months only. Waterproof mattress toppers should fit the mattress well and pillows and bumpers should never be placed in the cot due to the suffocation risk.

But if there's no safety standard, how can I actually test the firmness of the mattress?

Ron Somers, Former Director of Epidemiology, SA Health and a researcher behind the standard mattress firmness test explains how companies test the firmness of a mattress and he also shows how to replicate this simply and easily at home, using a few common household items - 12 CD’s (or DVD’s), 2 full 1L tetra pack cartons with a square bottom (eg milk or juice bottles), a ruler and a marker. You can also test how quickly the mattress springs back into shape when pressure is applied. If it springs back quickly this will likely be a safer option than one that isn’t.

Please note that this is an informal testing method for use in the home, but does provide a reasonable result in terms of knowing how safe your baby’s mattress is.

How to choose the right mattress size for your cot

If you’re buying a cot and mattresses separately you will need to choose a mattress that fits the cot frame tightly, with no more than a 2cm gap between the mattress and the cot frame. This is to prevent baby being caught between the mattress and cot.

When buying a cot in New Zealand, it must have a swing tag stating the recommended mattress size for that particular cot, along with the manufacturer’s name and contact details, so you can refer to this when shopping for your mattress. The manufacturer’s recommended sizing information should be permanently marked on the mattress base.

Additionally, the mattress also needs to be the right depth for your specific cot. If the mattress is too deep for the cot, the height of the railings is effectively lowered meaning the baby could fall from the cot. The cot you choose will determine the depth of mattress that can be used safely and this must be stated on the cot when it’s purchased, along with the manufacturer’s name and contact details.

Mattresses should be between 100 and 150mm thick but do not choose a depth greater than the maximum specifed on your cot.

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