A shortage of midwives has increased the risk that things may go wrong during childbirth, a study suggests.
Midwifes provide specialist care
Researchers, writing in the British Medical Journal, examined care at seven maternity units in north west England.
They found that all had staff shortages and most relied on agency staff.
Despite the lack of staff, the use of high-risk practices, such as giving labour-inducing drugs and performing epidurals was still commonplace.
During the study the researchers directly observed one adverse event and 15 near misses - most of which they concluded were related to staff shortages.
A decision was made to perform an emergency Caesarean on a woman with a low lying placenta
The baby had a slow heart rate
However, the procedure had to be delayed for two hours, as the five midwives on duty were too busy to assist in theatre
The baby survived, but was in poor condition
The researchers estimated that a near miss took place in one of the units every 2.5 to five days - and they also uncovered evidence that near misses went unreported in all units.
Lack of training
Staffing shortages were further compounding the problem by preventing people from taking part in training sessions.
And in six of the units midwives were forced to spend considerable amounts of time on clerical duties, instead of working directly with patients.
None of the units had contingency plans in place to deal with unexpected surges in demand for care that occur frequently on labour wards.
A woman with twins needed an emergency Caesarean
Three midwives would normally assist
However, although six midwives were on duty, all were busy elsewhere
The Caesarean was consequently delayed for an hour
During intensely busy periods, when shortfalls were most acute, senior midwives in charge of the shift were unable to provide support for inexperienced colleagues.
The researchers, from the Universities of Salford, Manchester and Sterling, stress that midwives are highly dedicated to their work.
But they say: "The system cannot operate safely and effectively when the number of midwives is inadequate, midwives are poorly deployed, and they are unable to engage in opportunities for training and updating.
"We observed many accidents waiting to happen."
Lead researcher Mrs Brenda Ashcroft told BBC News Online: "The modern labour ward can be a very intensive care area with a high number of complications and you do need midwives that are experienced."
She called for measures to reduce the pressure on midwives, such as reducing their clerical duties.
"We should also try to value and nurture midwives, and not to be too quick to blame them if something goes wrong if it is basically the result of them not being able to be in two places at once."
Dame Karlene Davis, general secretary of the Royal College of Midwives, said: "There are currently 5,000 less midwives practising than there were 10 years ago.
"Despite the fact that people are training and entering the profession in record numbers it simply doesn't compensate for the number of midwives leaving."
The government is looking at ways to raise the number of trainees and to encourage people to return to practice.
But the RCM believes that shortages will only be properly addressed when students are financially supported and the current pay scale for practising midwives has some relevance on the cost of living.
The Royal College of Midwives said one-to-one midwifery care throughout a woman's labour was vital to ensure a healthy outcome.
Dame Karlene said: "The high Caesarean section rate is a major cause of increasing midwives workloads and the rates tend to come down when midwives are able to spend time with women throughout their labour."
Shadow Health Secretary Dr Liam Fox said: "Midwifery under Labour, like nursing, has become a demoralised profession.
"Above all, staff feel less and less able to do the work they were trained to do in the way they want to do it - because they are forced to spend more and more of their time pursuing government targets.
"So it's little wonder that there is such a shortage of midwives."