Clare Cashion was 28 weeks pregnant and just about to board a plane home from a family Christmas in Ireland when her waters broke.

She was rushed to hospital in Dublin, where doctors managed temporarily to halt the birth. But there was no longer any question of her safely leaving the country, so while her partner and three older children flew back home to England, Clare stayed behind in hospital. Her son Cullan was eventually born on New Year’s Day by emergency caesarean section, after a labour that was traumatic from the beginning.

It was only when surgeons began operating, says Clare, that she realised the epidural didn’t seem have taken properly. “I could feel everything. I was screaming and they were saying, ‘No no, you can’t feel it, the epidural has worked,’ and I was screaming, ‘No, I can feel this, I can feel this.’” Her son was eventually born under general anaesthetic, weighing just 2lb 12oz (1.25kg): it was two months before she could return with him to her family in England, and only then did the full impact hit her.

“I thought, I can do this, I’m a mother of four. Just slap my face on, drag the toddler along to a mum-and-toddler group and take the baby. But inside I was a wreck. It’s not something people talk about, you’re just supposed to get on with it – the only thing you ever hear is: ‘At least you and the baby are OK.’ It’s the most frustrating phrase; you just want to scream and say: ‘Yes he’s alive and I’m alive but I’m not OK; physically, I’m OK, but mentally, I’m really not.’” She is still struggling with a deep well of anger over what happened, and with guilt about the impact it has had on her other children. For a while, she says, she parented almost robotically: “I’d do what I had to do, but I couldn’t say that I was present. I’d focus on silly things, like the house had to be spotless; I would over-control things because I had no control over what happened me [in hospital].”

Facebook Twitter Pinterest ‘Inside I was a wreck’: Clare Cashion with her son Cullan. Photograph: Sam Frost/The Guardian

In the end, she says, posting her story on Facebook proved the easiest way of telling friends what she was going through while allowing those who didn’t want to know the gory details to scroll past. But it was crucial to her, she says, that she was able to tell the truth. “If you’ve gone through something that traumatic and don’t talk about it it’s like putting a filter on life. And if you think you’re the only one it has happened to, you feel as if you’ve failed.”

It is stories such as this that help explain why the midwifery lecturer Catriona Jones unwittingly touched such a nerve, when she suggested last week that sharing of birth horror stories on social media might be a factor in fuelling women’s fear of childbirth. As Jones reportedly put it: “You just have to Google childbirth and you’re met with a tsunami of horror stories. If you go on to any of the Mumsnet forums, there are women telling their stories of childbirth – ‘Oh it was terrible’, ‘It was a bloodbath’. I think that can be quite frightening for women to engage with.”

Yet beneath the headlines about women supposedly being silenced – something Jones is adamant she never intended – lies a far more complicated, nuanced story about why birth trauma is so common in Britain and yet somehow manages to hide in plain sight.

For her part, Jones is clear that she never meant that new mothers should stop talking and posting about their experiences. “I didn’t say: ‘Oh, women need to stop sharing their stories.’ I wouldn’t be able to hold my head up high in any midwifery conference again if I’d said that,” she explains from her office at the University of Hull. If anything, she was arguing for the opposite: better maternity services to support fearful mothers-to-be, based on a mental health programme developed at Hull to detect and refer anxious women early in pregnancy. Social media may, she says, be “one of the factors” involved in that anxiety, with recent research from Canada suggesting higher levels of nervousness in women who had read lots of birth stories, although it’s unclear why (it’s possible that women who were already anxious are more likely to go looking, for example). But it is helping women deal with the fears that matters, regardless of where they come from.

I had extremely painful, extremely violent births – but it’s an extraordinary and human thing to go through

Yet the striking thing is that women were so ready to believe that a midwifery expert might want to silence them. The story seems to have struck a raw nerve precisely because so many women do feel under pressure to keep distressing birth stories to themselves, a burden for some reason not placed on survivors of other medical traumas.

Meanwhile, at the other end of the end of the spectrum, even women who have had perfectly straightforward birth experiences can feel inhibited about saying so in case they sound smug or insensitive. “You feel as if it’s almost something to be ashamed of, that you need to keep quiet about it; that you might be ostracising other women or making them feel bad about themselves,” says Clover Stroud, the author of a memoir about motherhood, Wild Other, who has five children and happily admits that she enjoyed all their births. “I think it’s a real shame, because you generally hear the worst things. The line is that it’s just an appalling, undignified, violent and terrible experience, and actually it is a violent and undignified experience – I had extremely painful, extremely violent births – but it’s an extraordinary and human thing to go through.” The more women hear of both good and bad birth stories, she argues, the better. Yet so many women seem to feel the raw and bloody truth should remain their guilty little secret; something to be hidden, not just from women who haven’t had children yet, but sometimes from other mothers, too.

The striking thing about research into fear of childbirth is that until recently, it was so sparse. It was not until 2000, when the psychiatrist Kristina Hofberg published a paper on the severe and morbid fear of childbirth known as tocophobia, that the term began to be recognised and researched; until then, it appears, women’s terror was regarded as being of little interest. Definitions are hazy, even now – it is estimated that between 6% and 25% of women might be tocophobic, depending on how it is defined – and at its most extreme, they may resolve never to get pregnant even if they actively want a family. Some will double up on contraception methods just to ensure it never happens; those who do steel themselves to get pregnant may experience such dread that they can’t enjoy it or plan for after the birth.

Facebook Twitter Pinterest Jenny Shotton, who was diagnosed with PTSD after the birth of her second child. Photograph: Graeme Robertson/The Guardian

“It becomes all-consuming, so people can’t think past it,” says Julie Jomeen, a professor of midwifery at the University of Hull. “One service user described it to us as as being surrounded by people who were all excited about their pregnancies, going out and buying baby clothes, setting up their nurseries, but they can’t engage with it – their fear is at a level where they don’t believe they are actually going to survive childbirth.”

The causes of tocophobia are still not well understood, although Hofberg found connections with past sexual abuse. But unsurprisingly, it is also far more common in women already traumatised by a previous birth.

For Jenny Shotton, eight months pregnant with her third child, even something as routine as going to hospital for an antenatal appointment can be enough to reduce her to tears. She was diagnosed with post-traumatic stress disorder (PTSD) after the birth of her second child, Eloise, three years ago; a very rapid induced labour left her daughter in an incubator and Jenny drifting in and out of consciousness. When she woke to an empty cot beside her, she was convinced her baby had died. This time round, she is hoping for a “peaceful” home birth with a midwife she trusts, and who knows her history; but even so, she is bracing herself for what might come afterwards. “I’m not worried about the birth: I trust that it will be whatever it’s going to be and I trust my midwife. But what I am scared of is what I’m going to be like after the birth whether I’m going to have depression again, or if something will trigger me.”

PTSD is a condition more closely associated with combat stress or survivors of terrorist attacks. Yet a staggering 20,000 women a year – about 4% of all new mothers – are estimated to experience it simply as a result of childbirth (for comparison, an estimated 9% of soldiers deployed to Iraq and Afghanistan returned with it). For some, the condition is triggered by an obviously traumatic event, such as a haemorrhage, or something happening to the baby. But in a surprisingly large number of cases, it follows what doctors would see as a perfectly normal birth. “There are some experiences you’d see as traumatic clinically, you’d think, ‘Oh, that’s terrible’, but the woman will walk away fine,” says Jomeen. “And there are other women for whom you’d think things have been straightforward but something has happened that will traumatise them.”

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One explanation is that even safe, clinically uneventful deliveries can still be a shockingly violent departure from women’s expectations or everyday experiences. According to NHS figures, 41.9% of mothers delivering last year experienced tearing. Over a quarter of labours ended in caesarean sections and about 12% in doctors using forceps or ventouse (essentially a suction cap over the baby’s head) to get the baby out. Inductions, when labour is artificially kickstarted rather than allowed to happen naturally, have risen from 20% of births a decade ago to 29% last year and are associated with stronger contractions and more rapid labours. What doctors regard as normal may feel anything but for the woman on the sharp end.

But the way medical staff react when something goes wrong can also be critical, according to Dr Rachel Fraser, a perinatal psychologist who experienced a traumatic birth herself with her first child and now counsels women who have had bad experiences. Research shows the impact of trauma on women can be reduced by caregivers who make them feel safe, which means not only being treated kindly by midwives but given a chance to process and talk through their emotions afterwards – the one thing so many women feel inhibited from doing.

Stacey Wilson was diagnosed with PTSD after a long, drawn-out labour ending in a forceps delivery. It took doctors almost an hour to resuscitate her daughter Adaline, now 15 months old, and the sight of her newborn daughter lying grey and silent stayed with her. Months later, she was still feeling driven to compulsively check the baby was breathing, going into her room up to 40 times a night; she still has nightmares, flashbacks and feels compelled to relive the experience over and over again in her head.

I didn’t go to the mother-and-baby groups because I was avoiding the “Ooh, how did your birth go?” conversation

It was, she says, an intensely isolating time. “I didn’t go to the mother-and-baby groups because I was avoiding the “Ooh, how did your birth go?” conversation,” she says. “What mums bond over is we’ve all been though it together, but you kind of put yourself on the sidelines a little bit. You don’t want to say something that they just won’t know how to respond to.”

Her lifeline was the Birth Trauma Association’s Facebook page, an informal support group of about 6,000 members where she finally felt able to let down her guard; she still posts there regularly, although mostly now to reassure new members that they, too, will feel better with time.

Anonymity has freed Mumsnet users to confess to things women were once too ashamed to talk about, from prolapses and incontinence to graphic tales of blood and gore and ravaged flesh. At the other end of the spectrum are blissed-out “freebirthers” who post back-to-nature YouTube videos of themselves giving birth in the wild without any medical intervention (Simone Thurber’s video of herself giving birth in a stream racked up 76m YouTube views two years ago).

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As it is the dramatic stories that tend to go viral, the risk is that the kind of birth experiences most women actually have – neither overwhelmingly awful nor amazing, but somewhere in between – are rather lost in the crowd.

“It’s either, ‘I gave birth in moonlight and it was orgasmic’, or, ‘It was the most horrific thing that ever happened to me’,” says Rebecca Schiller, a doula and the CEO of Birth Rights, an organisation that helps women assert their rights to choose how they deliver. “Both ends of the spectrum exist but most women have something more in the middle.”

Yet flawed as they may be, the free-ranging, candid conversations about birth unleashed by the internet may well be functioning as a safety valve.

“People need some kind of avenue to process what has happened to them and if you don’t get that from society, from health services, from an overstretched GP who has about 20 seconds to talk to you, you will find an avenue,” says Fraser. Even in a society that still doesn’t easily allow women to voice unspeakable truths about childbirth, perhaps there’s only so long they can be contained.

• Tell us about your difficult childbirth experiences

• This article was amended on 19 September 2018. An earlier version misattributed figures from the NHS to the Office for National Statistics. It was further amended on 9 October 2018 to include the full name of Dr Rachel Fraser alongside a contribution from her.