Scientists say they have found a possible genetic link in sudden infant death syndrome (SIDS), also known as cot death.

The study, led by the University College of London, was published in the journal The Lancet. It found that genetic mutations linked to the breathing muscles not working properly were common in children with SIDS.

“Our study is the first to link a genetic cause of weaker breathing muscles with sudden infant death syndrome, and suggests that genes controlling breathing muscle function could be important in this condition,” the study’s senior author Professor Michael Hanna said in a statement. “However, more research will be needed to confirm and fully understand this link.”

SIDS can cause unexpected death in an otherwise healthy child. It kills about 300 children in the UK and 2,400 in the US each year, mostly between the ages of two and four months. But the cause of the disorder has remained unknown, making treatment difficult.

In the study, they noted that fewer than five people in every 100,000 carried a mutation in the SCN4A gene that seemed to hamper breathing. But in 278 children studied (84 from the UK and 194 from the US) who died of SIDS, four of them had the mutation, compared to zero in 729 healthy control participants.

It’s thought that these genetic mutations contributed in some way to the cause of death, although it’s likely that they work in tandem with other factors too. The mutation could lead to weaker breathing muscles as it affects the cell that the gene is responsible for. If other factors hamper breathing, such as getting tangled in a bed or inhaling tobacco smoke, it could mean they can’t breathe properly.

“We are very pleased that leading researchers continue to try and identify the cause of SIDS, which leads to the death of around four babies every week in the UK,” Francine Bates, CEO of The Lullaby Trust, said in a supporting statement. “In the meantime, we urge all parents to continue to follow our safer sleep advice to reduce the risk of SIDS.”

These guidelines include making the baby sleep on their back for the first six months and not sharing a bed with the baby if you have drunk alcohol, taken drugs, or are a smoker. The NHS has a full list of guidelines to reduce the risk of SIDS.