Babies born in hospitals at weekends are at greater risk of dying, a new study has found.
Researchers studied more than 1.3 million births and found the death rate among babies delivered at weekends was 7.3 per 1,000 births - compared to 6.4 per 1,000 babies born on week days.
The team at Imperial College London theorised that if all babies were born on a Tuesday, the day with the lowest death rate, there would be 770 fewer deaths each year.
Professor Paul Aylin of Imperial’s school of public health said, according to the Independent: "In our [study] we tried to account for the fact that differences in rates of complications on different days may be due to chance, or that births on certain days are more complicated in some way.
"However, even after making these adjustments, we found the rates of complications vary on different days."
The study, which was published in the British Medical Journal looked at the numbers of stillbirths or deaths that occurred within seven days in hospital from 2010 to 2012.
Researchers took into account others factors, such as the mother's age and planned Caesarean sections which usually take place during the week.
As well as an increase in death rate, infection rates for mothers and injuries to the babies, (including anything from cuts to brain damage), were also found to occur more frequently at weekends.
The rate of readmissions for the baby within three days of birth was higher for babies born on a weekend (12.3 per thousand births) compared to those born on weekdays (11.8 per thousand births).
However, researchers have said they "could not identify the cause of the higher risks".
A spokeswoman for NHS England said: "Most mums say they get excellent NHS maternity care, but for a small number of families that is not the case and it's vital that we take every step to continuously improve quality and safety.
"We have commissioned a wider independent review of NHS maternity services, which will assess how best we can respond to England's growing birth rate and the need for well-staffed and safe services that give mums more say over their care."
"The study itself does not give a reason for why these 'effects' occur," commented Louise Silverton director for midwifery at the Royal College of Midwives (RCM).
"Midwifery and maternity staffing levels are the same on weekends as they are on weekdays. Midwives work across 24 hours, 365 days per year."
Silverton said maternity units are already working at full capacity with greater demand for care.
She said: "We are already 2,600 midwives in England alone. The authors of this report have a stressed that this study is just an observational study and that no 'definite conclusions' can be drawn about the cause and effect of weekend deaths.
"We need to make sure that we identify the 'possible causes' so we can continue to ensure women receive the best possible care for both them and their baby."
The study concluded: "Solutions will require extra resources and all our creativity, to determine what explains the apparent protective effect of week day delivery and how to extend these benefits to women who deliver at the weekend, and their babies."
Dr Helen Webberley, GP for www.oxfordonlinepharmacy.co.uk said this study highlights the fact that access to adequate emergency cover within the NHS does require experienced doctors to be available out of 'normal office hours' and this may be what is behind this shocking higher mortality.
She told HuffPost UK Parents: "The NHS provides excellent care for most of the people, most of the time, but over the weekend there will be less availability of senior consultants, open theatre space and emergency cover.
"Medical training has changed a lot over the years. When today's senior consultants were training, they were expected to do the very long hours that today's junior doctors are exempt from.
"But now senior doctors are having to provide cover for the less experienced juniors who just haven't had the same hours of training and exposure.
"There is no doubt that staffing within the NHS is reaching a crisis, and maybe more shocking statistics such as this are needed to highlight possible gaps in care."
Previous studies into hospital care have come to similar conclusions.
In September 2015, a study identified a higher risk of death in patients admitted to hospital on weekends - within 30 days than those admitted during the week.