Experts have called for basic checks about expectant mothers' previous mental health problems after a new report showed there has been no significant change in the number of indirect maternal deaths for more than a decade.
The report - Saving Lives, Improving Mothers' Care, which looked at figures from 2011-2013 - said there had been a "statistically significant decrease" in the maternal death rate, and deaths from direct causes continued to decrease. Sixty-nine women died from direct causes such as pregnancy complications.
There were 145 "indirect deaths" - which included medical and mental health problems - in the same period. One in 11 of the women who died during or up to six weeks after pregnancy died from mental health-related causes.
The report said the "indirect maternal death rates remain high with no significant change in the rate since 2003".
It added: "Coordinated action across a wide range of health services is required to address this problem."
Nearly a quarter of the deaths that occurred between six weeks and one year after birth were mental health-related. One in seven of those women died by suicide.
The report, which included surveillance information for 575 women, was compiled by MBRRACE-UK - a collaboration led from the National Perinatal Epidemiology Unit at the University of Oxford.
The report identified clear opportunities for improvement, said University of Oxford Professor Marian Knight.
She said: "Although severe maternal mental illness is uncommon, it can develop very quickly in women after birth and the woman, her family and mainstream mental health services may not recognise this or move fast enough to take action."
Professor Knight said as women were seen by doctors, midwives and nurses, there was a risk nobody would "join up the dots" amid worsening symptoms.
She said: "Completion of some basic checks early in pregnancy will help.
"All women should be asked about any previous mental health problems as this could provide an opportunity for an early warning of potential future issues.
"Staff in mental health crisis teams need to be trained to understand the distinctive features and risks of maternal mental illness if they are going to provide emergency care for pregnant and postnatal women."
Royal College of Midwives spokeswoman Louise Silverton said it was "most concerning" that medical and mental health-related deaths had not fallen.
She said: "These women with complex medical needs require good preconception care and additional support after birth."
Ms Silverton said every trust in the UK with maternity services should have a specialist mental health midwife.
She said: "We know that suicide is a leading cause of death in new mothers in the UK.
"Despite this, provision of perinatal mental health services in the UK is at best patchy, and in some areas, non-existent."
Ms Silverton also pointed out many maternal deaths involved economic or socially-deprived backgrounds and women in particular ethnic groups.
The report suggested women should be asked about domestic violence to avoid victims "falling through the cracks" between multiple agencies. This was a particular problem for women who misused drugs or alcohol, it said.
It also identified areas for improvement in the care of women with cancer and those at risk of blood clots, which was the primary cause of direct deaths.
Health Minister Ben Gummer said the Government had invested £75 million to bolster perinatal mental health services.
Last month, a national ambition to halve maternal deaths, stillbirths, neonatal deaths and neonatal brain injuries was launched.
Mr Gummer said: "We have also increased the number of midwives and health visitors and are making sure those staff that care for new and expectant mothers are trained to spot the signs of perinatal mental illness."
He added: "This excellent report shows how we can use these new resources to reduce maternal deaths."