Soft or firm bed? Which is right for co-sleeping?

When it comes to comfort in bed, personal preference nearly always comes first. Some people enjoy feeling comfortably “cocooned” by a soft mattress, while others find it claustrophobic and prefer more freedom of movement. It is highly subjective.

But comfort is not just about how a mattress feels. It also depends on how well your body is supported and whether you can turn freely during the night. For most adults, the best balance is a medium-firm to firm sleep surface. Large studies involving adults with back pain have found, for example, that medium-firm mattresses reduced pain and improved function compared with very firm mattresses. The well-known trial by Kovacs et al. in The Lancet found that medium-firm mattresses produced better outcomes than very firm ones. [1][2]

That does not mean the same firmness suits everyone. Weight, sleeping position and body shape all play a part. But it does show that the research does not support the idea that softer is always better. When it comes to co-sleeping in particular, there are also clear guidelines on what is appropriate.

What does the science say, in brief?

• Research involving adults: medium-firm to firm support preserves the spine’s natural curves better than soft cushioning, and often better than a very firm mattress. [1][2]
• For infants: major health authorities recommend a firm, flat and continuous sleep surface, rather than one that is soft, body-contouring or inclined. These include the American Academy of Pediatrics (AAP), the CDC in the US, the Lullaby Trust in the UK and the Danish Health Authority. [3][4][5][6]

The distinction is clear:

Adults can choose a soft mattress based on personal preference

Infants “must” sleep according to safety guidance

What is recommended for your usual sleeping position?

For people who sleep mainly on their back or front: most experts recommend a medium to firm mattress.

For people who sleep mainly on their side: if you spend more than 90% of the time sleeping on your side, a soft feel may be beneficial. If you switch between your side, front and back, a medium firmness is usually recommended.

“The most natural”?

Historically, people slept on relatively firm surfaces: wool-filled bases, straw mattresses, felt, blankets laid over sleeping platforms, or directly on the floor. Very soft, deep beds only became common with the arrival of modern materials such as springs, foam and multi-layer mattress toppers. It is not our bodies that have changed, but what we can produce.

So it is hardly surprising that:

1. many people actually sleep more soundly on slightly firmer surfaces, and
2. modern safety guidance for young children is closer to the “original” approach: firm, flat and free from gaps.

Co-sleeping: why large, firm, one-piece mattresses matter

Many families choose to co-sleep because it makes breastfeeding easier, brings everyone closer and helps nights run more smoothly. Authorities also recognise that parents will co-sleep, which is why today’s advice is often: “If you do it, do it safely.”

The same key points recur across countries:

1. Firm, flat mattress: the child must not sink into it. [3][4][5]
2. No gaps or openings: one large sleeping surface is safest, so the child cannot roll into a gap between mattresses or between the mattress and the wall. Danish co-sleeping guidance explicitly states that one large mattress is safest and that the child should have as much space as they would in their own bed. [6][7]
3. The child should have their own lightweight duvet or sleeping bag and plenty of clear space, rather than lying beneath adult duvets and pillows. [5][6]
4. Adults must be aware of risk factors such as smoking, alcohol, medication and extreme tiredness. If any of these are present, co-sleeping in the same bed is not recommended. [3]
5. Plenty of space: Danish sources, for example, recommend at least 140 cm when two adults and an infant share a bed. [7] At FamBed, we recommend 90 cm per adult and 60 cm per child for everyone to sleep comfortably.

The consistent message from the AAP, the Lullaby Trust, the CDC and several European sources is that it is not closeness to a parent in itself that makes co-sleeping dangerous. The danger comes from soft, uneven or split surfaces that can cause the child to sink in or become trapped. [3][5]

What makes FamBed a safe choice?

• 2 comfort options in one mattress: medium and firm - The reversible FamBed mattress has a medium side and a firm side, suiting most preferences apart from those who prefer a soft bed. We do not offer a soft option, as this would conflict with guidance from experts and public authorities.
• Large, continuous sleeping surface - no gap between two single beds for a baby to roll into
• Firm or relatively firm construction - so the child does not sink into the area where the adult is lying
• Space for the child to have their own "zone" with their own duvet or sleeping bag, as recommended in the guidance

This closely reflects the Danish position that, if you choose co-sleeping, one large, firm mattress is the safest option, as it avoids gaps and an overly soft sleeping surface. [6][7]

FamBed therefore supports the elements of international guidance relating to a firm, flat and continuous sleeping surface when co-sleeping.

References (further reading)

1. Kovacs FM et al. The Lancet (2003): Effect of firmness of mattress on chronic non-specific low-back pain. [1]
2. Radwan A. et al. Sleep Health (2015): Effect of different mattress designs on promoting sleep quality, pain reduction, and spinal alignment in adults with or without back pain. [2]
3. American Academy of Pediatrics (AAP) (2022): Sleep-Related Infant Deaths: Updated 2022 Recommendations for Reducing Infant Deaths in the Sleep Environment. [3]
4. HealthyChildren.org (AAP) (2025): How to Keep Your Sleeping Baby Safe: AAP Policy Explained. [4]
5. Centers for Disease Control and Prevention (CDC) (2024): Providing Care for Babies to Sleep Safely - “Use a firm, flat (not at an angle) sleep surface.” [5]
6. The Lullaby Trust (UK): Co-sleeping advice and safer sleep overview. [5]
7. The Danish Health Authority (2022): Preventing cot death: a leaflet for parents (firm mattress, own duvet, plenty of space). [6]
8. The Danish Health Authority (professional guidance for health visitors): Preventing cot death and an uneven head shape… (at least 140 cm, one large, firm mattress). [7]