A health-care supervisory body condemned a maternity unit after 10 women died there during childbirth.
Out of the 10 cases, 9 were due to system failures, weak leadership and a poor quality of care at the unit , in Northwick Park Hospital, north-west London.
A report that explained what happened to the women, all of whom died during pregnancy or within 42 days of giving birth between April 2002 and April 2005, invigorated the watchdog to renew its appeal to all NHS trusts to check they have robust systems for monitoring the safety of maternity units.
"The national average for maternal deaths as reported by Cemach (Confidential Enquiry into Maternal and Child Health) is one death per 8,775 maternities or 11.4 deaths per 100,000 maternities," the Healthcare Commission said.
"The maternal death rate for Northwick Park maternity unit (in the period April 2002 to March 2004) was 74.2 deaths per 100,000 maternities.
Marcia Fry, the commission's head of operational development, said: "This was a sad and tragic series of events. We hope this report at least gives some answers to the families involved.
"At the time of the deaths, the working practices at the trust were unacceptable. However, under special measures the trust has got its maternity services on the road to recovery."
A £19m investment to improve the maternity unit and the appointment of three new consultants, 20 midwives and a team of 10 recovery nurses, are the alterations done so far, according to the trust's chief executive, Mary Wells.
"Clearly this has been a tragic time for all the families and I hope the report provides them with a better understanding of what happened," she added.
"I would like to reassure them, and the local community, that lessons have been learned and that we continue to do all we can to avoid tragedies of this nature happening again."
A record of failings including poor working practices and quality of care was found by an investigation in the North West London Hospitals NHS Trust.
According to the commission, the hospital failed to diagnose and treat when a woman's condition changed suddenly. The junior staff was usually made to deal with the complicated cases. Resources to deal with high-risk cases were insufficient. Only few consultant obstetricians and midwives were there, inadequate devoted theatre staff were there.
The maternity unit ignored the mistakes made leading to them being repeated. As the seriousness of the situation was not recognised by the trust's board, even it was criticised.
The North West London Hospitals NHS Trust said that they had realised and improvements will be made.