Tens of thousands of mothers and babies in England were harmed by potential lapses in maternity care in the past two years, the BBC has learned.
More than 276,000 incidents were logged by worried hospital staff between April 2015 and March 2017 - the equivalent of one mistake for every five births.
Most were minor or near misses, but almost a quarter of the incidents led to the mother or baby being harmed - and in 288 cases there was a death.
Ministers said safety must be improved.
Health Secretary Jeremy Hunt told the BBC the figures were "shocking" and improving the way mothers and babies were cared for was a "top priority".
"Mistakes in maternity care can lead to heart-breaking tragedies for mothers and babies."
But he said it was encouraging hospitals were being honest as that would help prevent repeat problems.
However, childbirth charity NCT said the figures suggested maternity care was "in crisis".
The incidents have been flagged up under a voluntary reporting scheme run by the regulator NHS Improvement that staff are encouraged to take part in if they have concerns about care.
The potential lapses logged include everything from short delays getting medication or records not being completed properly to babies being deprived of oxygen and life-threatening complications not being diagnosed.
'We lost our daughter - we can't move forward'
Wendy Agius was already past her due date in June 2014 when she became concerned that her baby was not moving.
Over the next two days Wendy, 33, and her husband Ryan, 37, made repeated calls to the local maternity unit - a midwifery-led unit in Eastbourne - as well as making three visits.
Each time they were told everything was fine - even after Wendy collapsed at one point.
When they returned a fourth time, no heart beat could be found. Their daughter, Talulah, had died.
"It was devastating," said Wendy. "They just kept sending us home. We were treated like an inconvenience."
It later emerged on one visit their baby's heart rate had been incorrectly recorded and their symptoms should have led to them being invited in more quickly and seen by a consultant at an earlier point.
But established guidelines were not followed.
Since then, the couple have not been able to get pregnant again.
Ryan said: "It was the worst thing imaginable. We can't move forward. It is always there every day."
East Sussex Healthcare NHS Trust, which runs the maternity service, said it had apologised for the failings.
An internal review concluded it was not possible to ascertain whether the mistakes had led to Talulah being stillborn.
How have mothers and babies been harmed?
Of the 63,380 cases of harm, nearly 55,000 involved injuries or conditions that required no more than basic first aid, such as treating a mother who had slipped in the shower.
But there were 8,134 cases of more significant harm, including 479 which caused severe harm, such as permanent disability, and 288 deaths.
Records seen by the BBC show a range of problems, including:
- delays dealing with women who had suffered haemorrhages and other complications
- babies left brain damaged after being deprived of oxygen during birth
- babies not screened for infections, leaving them at risk of meningitis, blood poisoning and pneumonia
- heart rates incorrectly measured or recorded
- delays in emergency Caesareans, causing distress to the baby
- midwives requesting help from consultants too late or not at all
- women being told to stay at home or sent away from maternity units despite reporting potentially serious problems
Overall, a third of the incidents related to mistakes with treatments or procedures, while one in five was a result of problems with the admission, transfer or discharge of mothers and babies.
Some hospitals have seen a cluster of serious incidents
The figures also highlight how some hospitals have seen more cases than others, although NHS Improvement points out that being a high reporter of incidents may just be because a hospital is more transparent about its care.
Nonetheless, in a number of the cases there are serious concerns about services.
Seven babies and two mothers died at the Royal Oldham and North Manchester General hospitals, both of which are run by the Pennine Acute Hospitals NHS trust.
The trust said it now had new leadership, staff had been provided with extra training and more midwives recruited, and since the changes had been made there had been no more deaths.
Meanwhile, five mothers and four babies died under the care of Portsmouth Hospitals NHS Trust between 2015 and 2017.
The trust said it could not provide details of what had happened because of patient confidentiality.
An inquest into the death of another baby - in 2014 - highlighted major problems at the trust.
The baby, Rafe Angelo, died from oxygen starvation.
His mother had been transferred from a local birthing centre to Queen Alexandra Hospital, which is run by the trust, after complications developed.
But there were a series of delays in her getting treatment, including an ambulance crew's detour for a toilet break and no doctors or midwives to meet the ambulance on arrival.
University Hospitals of Leicester NHS Trust also saw 11 cases of severe harm during the period.
And hospital bosses had to apologise to a couple after their baby died in 2015.
There had been delays in the mother undergoing an emergency Caesarean, while the heart rate had not been properly recorded.
The trust admitted the baby could have survived if mistakes had not been made.
Central Manchester University Hospitals NHS Trust reported the most incidents, more than 5,000.
The trust runs St Mary's Hospital in the city, which reported nine deaths, two were mothers and seven babies.
The trust said lessons had been learned from the incidents.
'We will make maternity safer' - ministers
The government has set a target for halving the overall rate of stillbirths, deaths and baby brain injuries by 2025.
To help ensure lessons are learned, the Healthcare Safety Investigations Branch, set up earlier this year, will start looking at all cases of unexplained serious harm and death from next year.
The reports made to NHS Improvement - highlighted by the BBC - will feed into that system.
The idea of both systems is to ensure the NHS creates a learning culture so similar mistakes can be prevented.
But unions have said staffing is also an issue.
The Royal College of Midwives believes the NHS in England is 3,500 midwives short of what it needs.
Staffing has also been highlighted by the Care Quality Commission, which inspects hospitals.
In its review of services earlier this year, it warned staffing and the ability to provide one-to-one care during labour was a concern.
Half of maternity units are currently judged to be not safe enough.
Maternity is also the biggest cause of clinical negligence payouts, accounting for half of the cost of all claims.
Last year, £1.9bn of claims were made - a rise of 91% since 2004-05.
Abigail Wood, head of campaigns at childbirth charity NCT, said: "Maternity care is in crisis, staffing levels are dangerously low and midwives are being stretched to the limit."
Additional reporting by Tom Calver