When should I drop the cot mattress base in the UK?

What do EN 716 cot manuals actually say?

The trigger is a skill, not a birthday. IKEA’s Gulliver advice sheet (the same AA-2598773 file used on IKEA UK and other IKEA sites) says: the lowest position of the bed base is the position it calls safest, and to prevent falls the mattress base should be adjusted to the lowest position as soon as the baby is old enough to sit up. The UK Gulliver product page repeats: lower the cot base to the lowest level as soon as the child can sit up on their own. The cot complies with EN 716-1.

Which? (19 September 2025) also says: once the baby can sit up unaided, put the cot bed in its lowest position. The same Which? feature still mentions older retailer habits (highest base until about three months; lowest around eight months when pulling up). Those calendar lines are not the Gulliver / EN 716 sit-up sentence. The Lullaby Trust tells you to follow the manufacturer’s instructions and names BS EN 716-1:2017 for cots.

How do I drop the base on a typical UK cot?

1. 1
   Open the sheet that came with this cot Find the mattress-base paragraph. Some cots have two heights (IKEA Gulliver); some cot beds have three. The sit-up / lowest-base line is the one that matters, even if a shop blog lists 5–6 then 7–9 months.
2. 2
   Watch for sitting, not the month When the baby can sit up on their own, the Gulliver / EN 716 instruction is to use the lowest base. Do not wait for a second 'pull-up' birthday if the sheet already fired on sitting.
3. 3
   Take the baby out and strip the cot Remove bedding and the mattress. Which? assembly tips: loosen the sides before you slide the base, then retighten. Two adults makes a 120 × 60 cm base easier to hold level.
4. 4
   Refit the mattress and measure the rail From the upper surface of the mattress to the upper edge of the cot frame you need at least 500 mm on the lowest base (and at least 200 mm if you are still on the highest base). If the mattress is too thick to leave those gaps, the mattress is the wrong one for this cot.
5. 5
   Check footholds around the cot IKEA’s product warning: do not leave items in the cot or place the cot close to anything that could provide a foothold. Dropping the base does not cancel a chair, changing table or radiator used as a step.

What are the 200 mm and 500 mm figures?

Which? second-hand checks also say at least 50 cm between the top of the mattress and the top of the cot — the same 500 mm idea in centimetres. That is a depth check, not a used-cot inspection (this page is not a second-hand survey).

Why do retailer blogs invent 5–6 then 7–9 month steps?

Because three-position cot beds look like a staircase, shops write a staircase of ages. Which? itself still carries leftover calendar wording (highest base until about three months; lowest around eight months when pulling up) next to the sit-unaided instruction. EN 716 manuals do not owe those extra birthdays. If your baby sits at four months, the Gulliver sentence has already asked for the lowest base. If your baby sits at eight months, you drop then — not at a printed 5–6 month shop step.

A middle notch, if your cot has one, is only for as long as your manual still allows it. Do not keep a high base because a blog said 'newborn position until six months'.

Does a cot bed use a different drop rule?

Which? treats sitting unaided as the moment to use the lowest position on a cot bed too. Conversion to a toddler bed is a later job — Which? says when the child starts trying to climb out. IKEA Gulliver’s sheet: when the child can climb out, the cot shall no longer be used for that child; the same file describes conversion to a cot bed from about 15 months up to 20 kg on that model. Those are climb-out / conversion limits, not a reason to leave the base high.

What changes after the base is down?

The mattress and bedding rules do not change: firm, flat, waterproof, feet-to-foot or a sleeping bag, clear of bumpers and toys. Reaching in is harder, which is why some UK cots have a drop side with a lock — Which? notes the British standard was revised so a child cannot lower it. The Lullaby Trust still wants the same-room wording for the first six months; dropping the base is not a reason to move the cot to another room early.

In shortDrop to the lowest base when the baby can sit up. Keep 200 mm of rail on a high base and 500 mm on the low base. Shop age charts are not the EN 716 line. Read the sheet that came with your cot.