Many hospitals are not learning from potentially avoidable deaths or serious injuries of babies during labour, a new report suggests.
Around half of local investigations into stillbirths and neonatal deaths as well as babies who suffer severe brain injuries following full-term labour are "inadequate", the Royal College of Obstetricians and Gynaecologists (RCOG) said.
The majority of parents are not being invited to contribute to such reviews, while many are unaware that they have even taken place, the College found.
Health Minister Ben Gummer said that the findings were "unacceptable" adding that the NHS is expected to learn from every case.
The College has called for more robust reviews into these cases, particularly for more parental input to the investigations.
The report is the first in a series from data collected as part of RCOG's Each Baby Counts initiative, a UK-wide quality improvement programme which aims to halve the number of incidents of stillbirth, neonatal death and severe brain injury during full-term labour - when a woman is at least 37 weeks pregnant when going into labour - by 2020.
The document provides interim data on these incidents from 2015. Across the UK there were 921 cases reported including 654 severe brain injuries, 147 early neonatal deaths - when a baby dies in the first few days of life - and 119 stillbirths.
Each Baby Counts reviewers have so far assessed 204 of these investigations. They found that 27% of the reviews were "poor quality". And 39% of the remaining 73% of reviews - or 29% of all reviews - did not include any actions to improve care. In total, 56% of reviews were "inadequate", the College said.
It found that only a quarter of parents were invited to contribute to the investigation into the death or injury of their baby. Meanwhile one in four parents were not even told that a review was taking place.
Nicky Lyon, parent representative on the Each Baby Counts advisory group and co-founder of the Campaign for Safer Births, said: "Our son Harry suffered profound brain damage during term labour. After a difficult life of tube feeding, constant sickness, fits and discomfort, our son died of a chest infection aged 18 months. As a family we have been left devastated at the loss of our beautiful boy.
"In the days following Harry's birth we asked what had gone wrong, but we were ignored. It was only after submitting a formal complaint that we learnt that an investigation was already underway.
"It's hard to describe how upset, confused and angry we were - the poor communication and secrecy made a terrible situation so much worse.
"Patients and their families should always be at the heart of a review, and being included in the process would have made such a difference to our family."
Judith Abela, acting chief executive of the stillbirth and neonatal death charity Sands, said: "The death of a baby has a lifelong impact on families. Many believe their baby's death was not inevitable and opportunities were missed to save their child.
"We have been calling for a robust and effective review process for some time, including parental involvement in local investigations. Parents' perspective of what happened is critical to understanding how care can be improved and they must be given the opportunity to be involved, with open, respectful and sensitive support provided throughout."
Professor Alan Cameron, RCOG's vice president for clinical quality and co-principal investigator for Each Baby Counts, added: "It is clear that we need more robust and comprehensive reviews, which are led by multidisciplinary teams and include parental and external expert input.
"Stillbirth rates in the UK remain high and our current data indicate that nearly 1,000 babies a year die or are left severely disabled because of potentially avoidable harm in labour.
"When the outcome for parents is the devastating loss of a baby, or a baby born with a severe brain injury, there can be little justification for the poor quality of reviews.
"Only by ensuring that local investigations are conducted thoroughly with parental and external input can we identify where systems need to be improved. Once every baby affected has their care reviewed robustly we can begin to understand the causes of these tragedies."
Health Minister Mr Gummer said: "These findings are unacceptable. We expect the NHS to review and learn from every tragic case which is why we are investing in a new system to support staff to do this and help ensure far fewer families have to go through this heartache."
Louise Silverton, director for midwifery at the Royal College of Midwives, added: "This report clearly shows that improvements in the investigation process are needed.
"Each one of these statistics is a tragic event, and means terrible loss and suffering for the parents. We must do all we can to reduce the chances of these occurring. This report shows that this is not the case and improvements are needed as a matter of urgency," she said.