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Baby boxes are being promoted as a safe alternative to standard cots, bassinets and Moses baskets despite a lack of evidence on their safety, experts warn.

The cardboard boxes, which come with items like clothes and blankets and can be used as a bed, are offered to new mums in Scotland and parts of England.

The Royal College of Midwives wants the scheme rolled out across the UK, saying it offers a "more equal start to life".

But experts have raised concerns about how safe the boxes are to sleep in.

Writing in a letter to the BMJ, Prof Peter Blair and colleagues say that, as the evidence stands, the boxes should only be used as a temporary bed if nothing else is available.

The boxes, which come with a mattress, have routinely been given to every expectant mother in Finland since the 1930s.

Scotland started offering the free boxes to new parents last year, while some NHS Trusts in England have had pilot and full schemes in place for up to two years. The boxes are not offered by health bodies in Wales or Northern Ireland.

The Royal College of Midwives says the boxes can reduce the likelihood of babies sleeping unsafely, either on a surface like a sofa or with parents who smoke, drink alcohol, or take drugs, and would particularly benefit those born into deprived environments.

However, Prof Blair and colleagues, including representatives of the cot death charity Lullaby Trust, said there was a lack of evidence into how safe the boxes are for sleeping in.

Compared with cots, bassinets and Moses baskets, it is harder for parents to see their babies easily when they are sleeping in them, they warned.

And some boxes, particularly those that are not laminated, may potentially be flammable or leave babies more vulnerable to pets and young siblings if they are kept on the floor.

They are also too small for most babies older than three months and there is no evidence on how durable they are, particularly if they become wet or dirty.

'Keep an eye on baby'

Prof Blair, from the University of Bristol, told the BBC: "One of the things we've been encouraging in the last 25 years is just a bit more closer contact, closer observation. Forget this idea of having infants in a separate room early on.

"Always have the infant in a cot by the parental bed in that room. During day-time sleeps, if the infant wants a nap, try and have the parent in the same room as the infant while that's occurring.

"It's just this idea of observation just in case they get into difficulties. Sometimes you might not be able to do anything about it, sometimes you can, that's what we've encouraged."

Prof Blair said he thought baby boxes went "slightly against that" because they made it harder for parents to keep an eye on their sleeping babies.

Moses baskets, cots and bassinets are preferable to baby boxes and also have to meet recognised UK safety standards, he said.

Media playback is unsupported on your device Media caption What's inside Scotland's baby boxes?

The experts also argue that there is no evidence the boxes have helped Finland achieve some of the lowest rates of cot death (sudden infant death syndrome or SIDS) in the world, as has sometimes been claimed.

SIDS rates are equally low in neighbouring countries, such as Sweden and Denmark, where boxes are not provided, they say.

Prof Blair and colleagues say there should be more high-quality studies "to better understand how families use the cardboard baby box, and its safety implications".

'Best start in life'

Responding to the letter, the Royal College of Midwives pointed out that its position statement on baby boxes had acknowledged that there was limited evidence around them reducing SIDS.

It said that baby boxes needed to be safe, of high quality and the box and mattress should meet at least the minimum UK safety standards.

The Royal College of Paediatrics and Child Health said: "Whilst the evidence around the effectiveness of baby boxes is still being debated, what we do know is that they provide all parents with the essentials needed to give their newborn baby the best start in life."

Image copyright Getty Images Image caption Experts recommend that babies sleep in the same room as parents for the first six months

How to reduce the risk of SIDS

Place your baby on their back to sleep, in a cot in the same room as you, for the first six months

Don't smoke during pregnancy or breastfeeding, and don't let anyone smoke in the same room as your baby

Don't share a bed with your baby if you have been drinking alcohol, if you take drugs or you're a smoker

Never sleep with your baby on a sofa or an armchair

Don't let your baby get too hot or cold

Keep your baby's head uncovered. Their blanket should be tucked in no higher than their shoulders

Place your baby in the "feet to foot" position, with their feet at the end of the cot or Moses basket

Source: NHS website

Cat Somerville, from Edinburgh, has a four-month-old son who only sleeps in his box.

"We are getting ready to set up his cot but there is still room to grow in the box at the moment.

"He feels secure with it being high-walled and it's soothing for him as it's stimula free once he's put to bed.

"We place it on top of a very solid, safe Ottoman next to the bed and against the wall, and I look down into the box and can monitor his safety.

"I am so very pleased and grateful for the box."

Liz, from Wigan, was also given a box when her baby was born.

"We use it during the day downstairs but at night we have a Moses basket upstairs.

"We will probably only use it for a couple more weeks as my average-sized five-week-old is getting a bit long for it.

"I check it daily for signs of damage as my daughter has previously dribbled on the mattress whilst sleeping.

"The mattress and mattress cover supplied with the box is washable and no wet has damaged the box.

"I have two cats and three school-aged children and do not feel it puts my daughter any more at risk than leaving her in her Moses basket, pram, baby swing etc."

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