Pregnant women and new mothers across almost half of the UK do not have access to specialist perinatal mental health services, according to a group of 60 professionals and charities.
The Maternal Mental Health Alliance says that is potentially leaving them and their babies at risk.
The organisations have released a series of maps, external showing the availability of services to women across the UK.
Perinatal mental health services provide care for women who become ill during pregnancy or in the year after giving birth.
Hannah Newport has told Newsbeat that she was fine to start with after the birth of her boy.
"It was like a waiting for the day that was gonna come when he was going be born," she said.
"I think straight away I didn't feel how I thought I was going to feel.
"I was a bit in shock that this baby had arrived and was with me.
"I didn't remember saying I didn't feel like a mum because you do, because from the time they're born everything changes.
"I'd say I was fine and I didn't really show how I was feeling and I didn't really talk to my family and friends.
More than one in 10 women develop a mental illness during pregnancy or within the first year after having a baby.
If left untreated the illnesses can have a big impact on women and their families.
In the most serious cases, perinatal mental illness can be life-threatening with suicide one of the leading causes of death for women during pregnancy and one year after birth.
Hannah says she suffered panic attacks soon after having her baby.
"The biggest thing for me that happened was when I was due to go back to work, when it got to the really awful point I was experiencing really high anxiety.
"I returned to my GP again and I had been back and forth a few times and I just got to the point where I wanted an answer.
"I just wanted someone to say, 'Yeah, this is really normal' or 'No, this isn't quite right and we need to work something out for you.'
"I feel like if my GP had maybe recalled all the appointments I had over the two years, I was going back with the same symptoms and the same complaints and same worries.
"I just felt like I was an overanxious mum? I always wanted to be told, 'There's this great group you can access, why don't you speak to your health visitor and see what's available through them?'
"I didn't really get that feedback so that's why I ended up going alone.
"While respecting the GP saying there's something more to it, I really had the need in me that was like, 'I need to find something that will make me feel better, like I need to feel myself again.'"
Health Minister Dr Dan Poulter said: "Healthcare systems across the globe have prioritised physical over mental health in maternity for too long.
"We are making sure that all midwives receive mandatory training in perinatal mental health, so there are specialist staff available in every birthing unit.
"Readjusting this balance and making fast progress really is everyone's business."
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