The "shocking" cost of mental health problems among women in pregnancy and shortly after birth is running into the billions, a new report has warned.
Treatment for new mothers and those more than halfway through pregnancy is described as "patchy" by the study, entitled "The costs of perinatal mental health problems", with a claim the long-term cost associated with all the births in a year is more than £8 billion.
The report, by the London School of Economics (LSE) and Centre for Mental Health, argues that spending £337 million a year would improve the care for mothers in the perinatal period - during pregnancy and the first year after childbirth - bringing it to the standard required by national guidelines.
The report, due to be launched in Parliament tomorrow, is part of the "Everyone's Business" campaign led by the Maternal Mental Health Alliance (MMHA) and funded by Comic Relief.
It states that nearly three quarters of the costs of treating depression, anxiety and psychosis relate to impacts on the child rather than the mother.
Dealing with the problems costs the NHS around £1.2 billion, the report said, with other costs including loss of earnings.
Around half of the cases of depression and anxiety during the perinatal period are not detected, it states.
In July the MMHA released a series of maps showing that many pregnant women and new mothers across the UK do not have access to specialist mental health services.
Annette Bauer from the LSE, who is the report's lead author, said the findings show the mental health of mothers to be vital to the economy and in society.
"In order to protect the family's long-term health, intervention needs to start before the child is born, or shortly after because the potential benefits are very high and the costs could be fully recovered in a short time frame," she said.
MMHA chairman Dr Alain Gregoire said the issue can be tackled.
"Perinatal mental health problems are common and costly. They affect up to 20% of women at some point during pregnancy or in the year after childbirth and are a major public health issue impacting on both women and baby.
"The good news is that women recover when they get the right treatment. It is vital that all women, wherever they live get the specialist help they need."
Economic secretary to the Treasury Andrea Leadsom said: "Every baby in the UK deserves to have the best possible start in life. Supporting perinatal mental health within a parent infant relationship is critical to lifelong health and happiness for every child."