NHS England is spending £40m on doctors and other specialist mental health workers as part of its drive to help 30,000 more women by 2021.
At present, more than half of the country provides only basic services.
One in five women experiences severe depression or in some cases psychosis around the time of childbirth.
The funding will pay for more nurses and psychiatrists to provide specialist care for women in their homes and in maternity units, by giving advice on medication and lifestyle, counselling them and helping to minimise the risks to mother and baby if they become ill.
The money will also go towards providing buddying and telephone support from mothers who have had similar issues.
Some of the 20 areas to receive a share of the £40m include Bristol, Birmingham and Northumberland.
NHS England says another £20m will be shared out in 2017.
The childbirth charity NCT said the funding was welcome but there was still a long way to go to help all of the 140,000 women every year in the UK who suffer from mental health problems when they are pregnant or during the year after they give birth - known as the perinatal period.
Elizabeth Duff, NCT senior policy adviser, said their research found that only 3% of NHS local commissioning groups had a perinatal mental health strategy.
"We're particularly pleased to see plans to enable mothers who have experienced similar issues to help others.
"Peer support can be a really powerful way to further break the stigma around perinatal mental health."
Natalie Ellis, from Sheffield, began to hate everything about herself soon after her son Finn, now seven years old, was born.
She had suffered from depression before - but this was different.
A news story about pornographic images being taken of young children being abused had really upset her and she found she could not get the abuse out of her head.
She began to have other, more troubling thoughts - she started wondering if she could be capable of abusing her own son.
These intrusive thoughts would not go away, torturing her for nearly a year, and because she was too scared to tell anyone about them she spiralled into a terrible depression.
She admits: "I had a deep hate for myself. I thought I'd rather be dead than hurt Finn.
"I thought I was a monster."
When she went back to work, she found the courage to look up her feelings on the internet and discovered that they were a recognised symptom of post-natal illness.
The relief she felt was huge - "I broke down, ran out of the office and sobbed."
Her GP set up counselling and cognitive behavioural therapy and she went on to anti-depressants, but she says it was the online support which really helped turn her life around.
"The women on the PNI forum saved my life, because no-one judged me," she says.
"They were a massive support network."
NHS England is also announcing that anyone who walks through the doors of A&E in a mental health crisis should be seen by a specialist mental health professional within an hour of being referred.
They should also be properly assessed and the next steps for their care planned within four hours.
Health Secretary Jeremy Hunt said: "Patients in crisis and expectant and new mothers who are suffering from severe mental health problems need urgent support and care.
"So this investment is fantastic news and will help make sure patients get the care they need, when they need it."
Janet Fyle, professional policy adviser at the Royal College of Midwives, said there was still more to do to prevent some women with pregnancy-related mental illness having to travel miles away from their families when they were in crisis.
"The RCM would like to see a specialist maternal mental health midwife in post in every maternity unit and trained to the standards developed by the RCM," she said.
"We cannot continue to read the constant reports of the number of women killing themselves because they were not identified earlier and treated, or because of the lack of trained staff or as a result of lack of services - it's heartbreaking and we can do better as a country."
NHS England said it was commissioning four new mother and baby units for women affected by serious mental illness.
Twenty areas across England are to receive funding to provide more support for pregnant women and new mothers with severe mental health problems.