Babies ‘ born smaller if mum sleeps on back’

Pregnant women who sleep on their backs are three times more likely to have a baby with a low birth weight, research suggests.

the position cuts blood flow to the womb – stunting foetal development, according to the study of 1,760 women.

It found ‘supine sleepers’ – the technical term for lying face up – had babies that weighed an average of 5oz less.

Sleeping on the back has already been linked to an increased risk of stillbirth and the nHS advises pregnant women not to sleep on their backs after week 20.

But the research suggests that the message may not be getting across. all the participants in the study completed a questionnaire that asked about their sleeping practices in the final months of pregnancy – the third trimester.

those who adopted the supine position were 3.23 times more prone to having an underweight child. the average size of babies of those who adopted the supine pose was 7.5lb – compared with 7.8lb for the rest.

an alarming 11 per cent of the their children were small, compared with 4.5 per cent for those who slept in other positions.

Professor Lesley McCowan, study author and gynaecologist at auckland University in new Zealand, said: ‘a reduction in birth weight associated with third-trimester back sleeping is clinically significant, biologically plausible and likely modifiable.’

Low birth weight babies struggle to feed, gain weight, fight off infections and can develop breathing difficulties. Supine sleeping has been shown to reduce the amount of blood pumped out of the heart – meaning a foetus gets less.

the research, which is published in JaMa network Open, is the first to identify the link between sleeping and weight.