How to Choose Baby’s First Mattress: The Ultimate Cot Mattress Buying Guide

Whether you’re a first-time or experienced parent, knowing how to choose the best cot or cot bed mattress for your little one can be quite the task. With so much variety and a wealth of advice from all corners of the internet, it can often be a case of information overload.


With new-borns spending on average between 8 and 18 hours a day sleeping (NHS), it’s understandably one of the most important purchases you’ll make for your little one. With over 12 years’ experience behind us, we’d like to think we know our stuff. This is why we’ve created this baby mattress buying guide to help you understand the basics behind buying and caring for your baby’s mattress.

So, what do you need to consider when buying your baby’s first mattress?

The Perfect Fit

Ensure your baby’s mattress fits perfectly in their sleep space. Whether it’s a crib, cot, or cot bed, the right mattress fit is a key component of sleep safety for your baby.


Cot Mattress Sizing

When buying a mattress for your child’s cot or cot bed, you must ensure a snug fit. Ideally, the gap between the mattress and the cot should be no more than 1cm wide to prevent your little one from trapping their fingers.

Alongside width measurements, mattress depth needs to be considered too. So how thick should a cot mattress be? Mattress depth should be double-checked with the manufacturer of the cot/cot bed. Most cots will come with a user guide detailing recommended mattress sizing.

The space between the top of the mattress and cot should also be enough to prevent your child from attempting to climb out.

Mattresses Sizes

Moses Basket: 28 x 74cm, 28 x 75cm, 30 x 66.5cm
Crib: 40 x 75.5, 38 x 89cm, 83 x 50cm, 44 x 80cm, 36 x 80.5cm, 57 x 72cm, 81 x 42cm
Carrycot/Pram: 30 x 67.5cm, 32 x 75cm, 34.5 x 76cm, 30 x 76cm, 30 x 72cm, 32 x 78cm, 33 x 82cm, 28.5 x 72cm, 27 x 70cm, 28 x 71cm, 30.5 x 74.5cm
Cot: 60x120cm, 68x122cm, 70x132cm
Cot Bed: 70x140cm, 68x117cm, 132 x 77cm, 69x139cm, 70x160
Single Bed: 90x190cm, 90x200cm

What Are the Different Types of Baby Mattress?

First things first, what’s the difference between the different types of baby mattresses on the market, and why should you care? .


Different materials will provide varying levels of support for your little one, as well as their own list of pros and cons with regards to mattress care.


Foam mattresses, for example, are usually the cheapest. Though usually very lightweight and easy to clean, they are known to lose their shape after several years. Foam is also generally considered less breathable than other materials, and can get clammy in warmer weather.


Sprung baby mattresses usually consist of a coiled spring interior with various layers of padding, natural or otherwise. They provide generally provide more progressive support for your little one than foam mattresses


Natural mattresses are one of the firmest varieties of baby mattresses, providing optimal support as recommended by safe sleep experts. They are also made without the use of any chemical nasties, and are naturally fireproof thanks to the breathable wool, which also helps regulate your baby’s body temperature.

Natural Organic Cot Bed  Mattress

Organic Cot Bed Mattress

From £239.95

Natural Organic Crib Mattress

Natural Crib Mattress

From £69.95

Materials Matter

At The Little Green Sheep, we believe what’s inside counts. Our award-winning mattresses are handmade using the finest natural materials.


When it comes to picking the perfect baby mattress, what materials are on offer?


Wool is the magic ingredient in our mattresses that helps to provide the best sleep environment for your little one. Wool is also naturally anti-allergenic, as well as temperature-regulating, which is a huge benefit for new-borns, as they cannot regulate their own body temperature until they are 3 to 4 months old. It is also a natural fire-retardant, meaning that our mattresses pass British Fire Safety standards without the use of any fire chemicals

 Natural Latex

Born as sap from the Hevea Tree, the natural latex in our mattresses works like a natural glue to bind the coconut fibres, or as a layer of natural foam to add an extra layer of comfort to the mattress.

Coconut Fibres

From the husk of coconuts, coconut fibre makes the perfect material for forming the sturdy core structure of a mattress. Rather than individual springs, layers of coconut coir act like thousands of tiny natural springs to reduce pressure points and provide even support


Compared to more synthetic covers, a cotton cover offers added breathability to your mattress. It’s also super soft against baby’s delicate skin, so they can sleep comfortably time and time again.

Cot Mattress Breathability

It’s important to ensure the cot or cot bed mattress you invest in is highly breathable, as this will help your little one with temperature regulation and sweat-wicking, ensuring a warm, dry sleeping environment for your baby that will keep the dust mites away.

Air-permeable by design, our mattresses are made with naturally breathable materials that allow for maximum airflow.

Organic Cot Bed Mattress

Natural Organic Cot Bed Mattress

From £239.95

Natural Crib Mattress

Natural Organic Crib Mattress



According to Babycentre, newborns tend to sleep between 16-17 hours a day on average. With this much time spent snoozing, it makes sense to invest in a sturdy yet comfortable mattress that will offer your little one the support they need. Mattresses with dual firmness are a popular option, and offer long-lasting, customisable support as your little one grows.

The Little Green Sheep Twist mattress is part of our best-selling range, backed up by countless awards over the past 8 years.

The firm side provides optimal support for babies up to 12 months, as recommended by safe sleep experts. When baby becomes a playful toddler, you can simply twist the mattress for a more supple, comfy and durable support that will last for years to come.

How Long Do Baby Mattresses Last?

Our Twist and Organic Cot Bed, and Single mattresses all come with a 5-year guarantee, for years of comfort and support as your little one grows.

Basic Mattress Care

To ensure your mattress lasts as long as possible, it’s essential you exercise some basic mattress care to keep it in tip-top shape. We recommend airing your mattress a few times a week by removing any covers until you next use it.

How Do You Clean A Baby Mattress?

To clean, be sure to wipe down or hoover the surface of the mattress when needed. If you do wipe it clean, be sure to allow the mattress time to air dry fully before use.

Mattress Protectors

Always use a mattress protector – we recommend our award-winning, 100% waterproof mattress protector to keep your mattress in the best possible condition, and protect it from accidents or spillages. Made from organic cotton, with a thin polyester membrane for waterproofing, it’s also super soft, without that plastic or crinkly feeling that’s often a hallmark of other protectors.

When possible, we recommend regularly turning your baby’s mattress to increase longevity, as this will prevent it from wearing out too much on any given side.

To Reuse or Buy New

Ideally, it’s recommended that parents buy a new mattress for each child. If, for whatever reason, this is not possible for you, ensure the mattress you reuse is one you know the history of, that is clean and in suitable condition.

Our Guarantee

At The Little Green Sheep, we’ve dedicated ourselves to creating the most natural sleep environment for your baby. All of our mattresses are sustainably made in solar-powered factories to the highest standard to ensure only the best night’s sleep for your little one.