The practice of swaddling babies, which has become fashionable as a way to calm them, risks causing them hip problems as they grow, doctors warn.
Parents have been turning to the old-fashioned practice in order to settle their babies and help them sleep better. Swaddling, which involves wrapping the baby in sheets or blankets with their legs out straight and arms pinned so that they cannot move, has been shown to induce sleep and soothe excessive crying and colic.
But, say doctors who specialise in orthopaedics, evidence shows that the practice increases the risk of developmental hip abnormalities. Professor Nicholas Clarke of Southampton University hospital writes in the journal Archives of Disease in Childhood that one in five babies are born with a hip abnormality, perhaps because of a breech birth or family history. Although these can resolve unaided, swaddling can delay it.
Swaddling has become more popular, says Clarke. Nine out of 10 infants in north America are now swaddled in the first six months of life. Sales of swaddling clothes increased in the UK by 61% between 2010 and 2011.
But studies have shown that babies who do not have their legs free to bend and kick can suffer dislocation or abnormal development of the hip.
"A high incidence of hip dislocation was reported in Navajo Indians who strapped their infants to a board," Clarke writes. "In Japan, an educational programme initially aimed at grandmothers was commissioned to prevent traditional swaddling." The programme cut the incidence of hip dislocation from between 1.1% and 3.5% to just 0.2%.
Clarke says that parents should be advised on "safe swaddling" if their babies are at risk of hip development problems. "In order to allow for healthy hip development, legs should be able to bend up and out at the hips. This position allows for natural development of the hip joints. The babies' legs should not be tightly wrapped in extension and pressed together."
Commercial products for swaddling babies should have a loose pouch or sack for the legs and feet, allowing plenty of room for movement, he says.
Other experts agreed with him. "There is indeed evidence that swaddling can affect the normal development of infants' hips," said Andreas Roposch, consultant orthopaedic surgeon at Great Ormond Street hospital.
"Similar effects may be seen in all devices or manoeuvres that place the legs in a purely straight position for prolonged periods in this critical age of early infancy. Swaddling should not be employed in my view as there is no health benefit but a risk of adverse consequences."
Dr Alastair Sutcliffe, reader in general paediatrics at the Institute of Child Health, University College London, said swaddling had been known to be associated with an increased risk of congenital dislocation of the hip (CDH) for many years.
"The archetypal example is in traditions where a baby is carried with their legs splayed around a mother's waist such as in Nigeria, where there is a virtually unseen rate of CDH, whereas in a country where swaddling is employed, such as far-eastern countries, there is a much higher rate of CDH.
"I would advise that if a baby needs to be wrapped up to get off to sleep that parents do this in a sympathetic and loose manner, not tight, especially around the babies' hips."
