The idea that lying down while giving birth is a bad thing has been challenged by researchers
Women are often told to stay active in labour or adopt upright positions to prevent slowing down delivery, ease pain and reduce the chance of needing intervention such as forceps.
But a new study has found that women are actually more likely to have a natural birth without any intervention if they lay on their side rather than staying upright.
The length of labour was also slightly shorter when women were lying down and they were no more likely to need a ventouse or forceps delivery, Cesarean section or to suffer tearing.
The study, the largest to date on the issue, examined 3,093 first-time mothers having a low-dose epidural.
At present, UK guidelines say women having an epidural should stay upright in the second stage of labour to reduce the chance they will need ventouse or forceps.
But the new study questions this and its experts also plan to replicate the clinical trial in women not having an epidural.
They said the current evidence suggesting lying down is bad was of poor quality.
Professor Peter Brocklehurst, from the University of Birmingham, who worked on the study, said: “We are now designing the next trial to look at position in labour among women without epidural.
“If you look at the evidence saying upright is best, then yes, it should be questioned.”
But Prof Brocklehurst warned women not to lay flat on their backs in labour.
He said this was known to cause distress to the baby and should not be recommended.
The new randomised controlled trial, published in the British Medical Journal (BMJ), looked at women who gave birth in 41 UK hospitals between October 2010 and January 2014.
Women were randomly allocated an upright or lying down position (lying on the left or right side) during the later stages of labour.
The study found there were fewer spontaneous vaginal births in women in the upright group (35.2%), compared with women in the lying down group (41.1%).
Professor Brocklehurst said researchers could only speculate on the reasons why lying down increased the chance of a spontaneous vaginal birth.
“However, the evidence we have found from this large trial group provides an easy and cost-free intervention in our labour wards,” he said.
“Pregnant women, in consultation with their healthcare providers, can now make informed choices about their position in the second stage of labour.”
He said that given the clear benefit of the lying down position, “perhaps all women who have an epidural should be offered the choice of adopting a lying down position in the second stage until we know otherwise”.
The study was funded by the National Institute for Health Research.