When Mary discovered she was pregnant, she was more than delighted: she was relieved. It was 1981 and although she was just 23 years old, she had wanted a family since she had married three years earlier.

“Expecting our first child was the best thing ever,” Mary (not her real name) tells me from her home in Ireland, her voice softening at the memory. “It was what I had always dreamed of.” Her friends and her three sisters, already mothers themselves, reassured her giving birth was just “aches and pains”, she says. But for Mary – now a lively, funny healthcare worker – it was the beginning of a devastating experience that still affects her 30 years later. And the problems weren’t the natural complications that can trouble any pregnancy. They were the result of a doctor’s intervention.

“I was in labour, but for a long time,” Mary remembers. “I was in so much pain that I was shouting and roaring. I was hysterical. I remember a nurse slapping my jaw and telling me to get a hold of myself. At one stage, my heartbeat and the baby’s heartbeat got them worried. So they called a doctor to examine me.”

When the doctor arrived, he did something Mary cannot forget. “They gave me gas and air and an injection, and took me to another room, where they tied my legs up on each side,” she recalls. “There were two nurses on each side of me. I saw this doctor at the end of my bed with a big, long silver thing. They made a hole in your private parts, and he inserted this silver thing up and cut the pubic bone and pushed it over to widen your pelvis for you to deliver your baby yourself.”

Petrified and in agony, Mary had been subjected to a symphysiotomy – a controversial operation that was seldom used in the rest of Europe after the mid-20th century, but which was carried out on an estimated 1,500 women in Ireland between the 1940s and 1980s.

The procedure involves slicing through the cartilage and ligaments of a pelvic joint (or in extreme cases, called pubiotomy, sawing through the bone of the pelvis itself) to widen it and allow a baby to be delivered unobstructed.

Critics blame the continued use of the operation on a toxic mix of medical experimentation, Catholic aversion to caesarean sections and an institutional disregard for women’s autonomy. They claim it has left hundreds of surviving women with life-long pain, disability and emotional trauma. For some in Ireland, it is yet another scandal perpetrated against women and girls, joining revelations over the Magdalene laundries (where “wayward” women were abused), the deaths of children at mother-and-baby homes and sex abuse in the Catholic church.

Not everyone agrees with this analysis: some doctors and historians argue that these criticisms fail to account for wider changes in medical culture. But this year the mothers who believe they were wronged finally got some encouraging news. In July, the UN Human Rights Committee called for the Irish government to hold an investigation into the issue. And last week saw the deadline pass for applications to the state’s ex gratia redress scheme, which offered women who have been through the procedure compensation sums of between £40,000 and £120,000. More than 300 women are said to have applied.

Their supporters say the moves are not before time. Mark Kelly of the Irish Council for Civil Liberties says that, despite having interviewed victims of torture, “this remains just one of the most appalling things that we have come across”. Nigel Rodley, chair of the UN Human Rights Committee, called the use of the operation without patients’ informed consent a “systematic assault”.

For Mary, the extreme pain that the symphysiotomy left her in was compounded by the anguish of not knowing if her baby daughter – who was eventually delivered by vacuum extraction – would survive.

“They rushed her off to special care, so I never even got to see her,” she says. For five days, the new mother was ordered to lie completely flat with a corset around her hips to give her pelvis a chance to heal. For days she was unable to see her daughter in the special care unit because there was no lift.

Although she was allowed home two weeks later, Mary says the long-term effects of the operation on her own health have been catastrophic. “I hold down a job, but only because of the painkillers,” she says. “I have arthritis in my hip and in the bottom of my spine. I walk with a limp. No one can help – there’s no way back. Getting up and down stairs or getting up on a chair I can’t really do. You get one leg up, then the other slips down.”

The worst problem, she says, is incontinence. “I wear pads the whole time, and have been since the age of 23. My sisters all had babies and none had this problem. A lot of people might have a little leak, but this is a whole flow … It’s very embarrassing.”

Mary and her husband went on to have three boys as well as their daughter. She believes she should have been offered a caesarean section much earlier. But campaigners and historians say it was exactly to avoid caesarean sections that symphysiotomy was used in Ireland.

Symphysiotomy was first used in the 19th century. As caesarean sections grew safer, the use of the operation declined in the developed world. But Alex Spain, the master of Dublin’s National Maternity Hospital (NMH) until 1948, disapproved. According to Jacqueline Morrissey, a historian who began investigating the practice in the 1990s, it was Spain’s Catholic beliefs, not his medical judgment, that guided his actions. At the time, the established medical consensus was that having more than three caesarean sections was dangerous, and that further pregnancies would have to be stopped by sterilisation or contraception. Spain considered this unacceptable, says Morrissey, and talked about “the mutilating operation of sterilisation and marital difficulty”.

Morrissey quotes Spain as writing that “the weight of the entire English-speaking obstetrical world” was against symphysiotomy, due to the belief that it carried a higher risk of infant mortality than a caesarean; nevertheless, Spain would lead its revival among the maternity hospitals of Dublin.

His successor, Arthur Barry, was even more opposed to contraception – refusing to allow women whose lives were at risk to be given advice on “natural”, Catholic-approved methods. This, Morrissey points out, put him “well on the conservative side of the church, and the pope”.

The use of symphysiotomy went beyond the emergency of “obstructive” births. It was sometimes used in pregnant women who were believed to have pelvises too small for the size of their baby, and in an estimated 3% of cases, after a caesarean section, to allow subsequent children to be delivered vaginally. In 2012, Olivia Kearney, who was subject to a post-caesarean symphysiotomy when she was 18, was awarded €325,000 (£256,000) in damages for this “grave medical malpractice” when no medical justification for it was found in her notes.

By 1966, a new master had taken control of Dublin’s NMH. Symphysiotomy declined, and the hospital started to give family-planning advice. But former students of the NMH continued the practice elsewhere. In Our Lady of Lourdes hospital in Drogheda in the north-east of Ireland, it survived well into the 1980s. Marie O’Connor, the chair of Survivors of Symphysiotomy, who has written a book about the scandal, says the continuation of the practice was also driven, in the absence of clinical necessity, by the need to train students in hospitals like Lourdes so that the surgery, which did not require electricity, could be carried out in rural parts of Africa and elsewhere.

For 88-year-old Rita McCann, however, the change in practice came too late. She had her first baby at the NMH in December 1957; 60 years later, she says, she still has nightmares.

“You blank a lot of it out, over the years,” she tells me simply, from her home in County Monaghan, “but you don’t forget. It gave me the horrors.”

She went into labour on 15 December, but was left alone for 36 hours. She was then taken into a room that soon filled up with medical students and doctors. “I was pulled to the bottom of the bed and my legs were put in stirrups,” she remembers. “I couldn’t see anything because I was lying on my back. They were very silent and I was scared stiff. I didn’t know what they were doing. Then my left side went into a spasm and I was in agony.”

No one told Rita, a florist, what was being done to her, and she assumed it was a caesarean section. “I was listening for the baby’s cry, but I didn’t hear anything. There was a doctor sitting upside my head – probably to restrain me – and I asked him, ‘What about the baby?’ And he just said, ‘Oh the baby won’t be born now,’ which rather shocked me. I asked no more questions.”

Eventually, Rita was put under a general anaesthetic and her baby was delivered using forceps. Even then, she couldn’t see him for two days. Although her husband and sister reassured her, she was terrified. “I thought something had happened to the baby and nobody was telling me,” she says.

For six months, she was in agony, unable to walk without pain or to carry her baby safely. She moved back to County Monaghan to live with her parents. Despite all that, at her six-week check-up, she told the doctor that she was fine. “There was no way I was going back in the hospital,” she says. “I was so frightened. I wasn’t taking the risk that he would take me in again.”

Along with her lower-back pain, Rita believes the trauma had other life-changing effects. “My second pregnancy ended in a miscarriage, and I am sure it was just pure terror,” she tells me sadly. “I was so scared about going through childbirth again.”

Perhaps the most shocking aspect of the women’s stories is the lack of consent. “These operations were covert, and the women were generally not informed it was going to happen,” stresses O’Connor. “The vast majority left hospital without knowing their pelvises had been broken. Many did not find out for decades. This was a mass medical experiment, and the doctors didn’t really study the long-term side-effects. In many cases it destroyed lives.”

There are some who tell a different story. Dr Michael O’Dowd, a former chair of the Institute of Obstetricians and Gynaecologists, rejects the theory that the use of symphysiotomy was the result of an unholy alliance between medical ambition and religion. While the institute, formed in 1976, has issued apologies to the surviving mothers and their families, he says the doctors involved “were trying to help. Hurting people is not a doctor’s primary focus.”

O’Dowd and other experts, such as Nynke van den Broek, the head of the centre for maternal and newborn health at the Liverpool School of Tropical Medicine, say medics may have had good reasons for looking for alternatives to caesarean sections because they were far from the routine, relatively safe procedures of today. Van den Broek also notes that recent medical papers suggest symphysiotomy is a relatively low-risk operation to use in emergency situation in low-resource settings.

Religion, O’Dowd says, played a part, because of the laws of the country and patients’, as much as doctors’, beliefs. Also, he points out, even in the 1980s the medical culture of taking consent from patients was much softer. “There was implied consent to do what was best, because [patients] might not know as much as you know. That’s not necessarily true now.”

It’s a view echoed in a government-commissioned report by historian Oonagh Walsh, which concludes that symphysiotomy “was considered the most suitable thing to do in order to obey the laws of the time”, and was favoured in the 1940s and 1950s because “the safety of repeat caesarean sections was unproven”.

Morrissey, however, takes issue with this, saying the Walsh report uses NMH master Arthur Barry’s discredited reports, in which he omitted cases in which children had died; she also says the issues around contraception were not as clear-cut as O’Dowd suggests.

The real argument, according to Mairead Enright, a law lecturer at the University of Kent who specialises in religion and law, is whether medical staff were negligent in using “a procedure so inherently defective that any doctor should have realised it was wrong”.

“The consequences for women afterwards were so severe that they should have known it was not the proper way to go,” she argues. “Depriving a woman of one medical treatment, which has problems, and substituting another that has guaranteed morbidity to circumvent contraception is gender-based violence.”

The one thing all sides agree on is that too little investigation has been done. The government’s redress scheme does not match the UN Human Rights Committee’s call for an independent investigation that would “prosecute and punish” the perpetrators, while offering “adequate compensation and rehabilitation on an individualised basis”.

In fact, says O’Connor, the scheme that opened this month explicitly rules out accountability, thanks to the long list of institutions and individuals – doctors, medical missionary orders and hospitals – mentioned on the legal waiver that the women must sign in order to be eligible for the money.

With the scheme only open for 20 days, O’Connor says many women have had trouble accessing their records, and are unlikely to get more than the lowest payout. Days after the redress scheme closed, a huge tranche of records from Airmount hospital were discovered.

O’Dowd, too, thinks not enough has been done. He would like to see scientific research into the women’s health problems to see what could be directly related to the operations, and to give the women the individual care they need. His suggestions, he says, were rebuffed by Survivors of Symphysiotomy, one of three survivors’ groups, who feared it would be not sufficiently independent. “I have a mother, wife and grandchildren, and through my own illness I know what it is like to meet medical staff – some are sympathetic and some aren’t. I wanted to help the women and their families.”

Two of the smaller survivor groups have supported the scheme, saying their clients want a “non-confrontational, humane and speedy process”. But next month the cases brought by survivors will be up in Ireland’s High Court. Many say that, despite their age, they will not stop their fight for justice.

Rita McCann is clear about what needs to be done. “I feel extreme anger that it wasn’t explained, we weren’t given any options,” she says. “No one has taken responsibility. When I met other women it was so hard to listen to their stories – some had lost babies. No one could talk about it without dissolving in tears. I want an apology and an explanation – the explanation should have been done before they ever put a knife into us.”