She had planned to give birth at home, unassisted, but her uterus partially ruptured during labour, almost killing her. For a month, she was confined to bed, barely able to move, let alone look after her family.
The doctor said it would be reckless for her to conceive any more children. But when she turned to her friends, they offered bleak counsel, backed with the force of the Bible. "I was told that a woman shouldn't shrink back from supposed dangers and that we should honour God with our bodies," she says. "Jesus died for us, we should be willing to die for him." She became pregnant twice more, suffering two miscarriages.
Garrison and her husband, Warren Bennett, had originally decided to stop at three kids. He had a vasectomy, to make sure. But after reading The Way Home, by Mary Pride, they decided to reverse the procedure – calling one of the doctors helpfully listed inside the back cover. In the next six years, they had four more children.
Pride's book is one of the founding texts of the Quiverfull movement, which encourages Christians to refrain from using all forms of birth control, including abstinence. It believes child-bearing women are like missionaries, to be commended for their courage and sacrifice.
"I had it all calculated out," Garrison says. "I had seven kids and they were each gonna have 12. They were all going to continue in the faith, to be warriors for Christ."
Calvinist pastor Doug Phillips, whose Vision Forum Ministry provides spiritual guidance, educational materials and an online catalogue of approved activities and clothes, has eight children. He preaches that Christianity can only triumph over secular liberalism if believers practise "multi-generational faithfulness" by raising an army of devout soldiers. His 200 Year Plan envisages a godly United States, six generations from now, with fundamentalist evangelicals in the majority and a theocratic government in charge.
The key to the concept comes from the Bible, in Psalm 127: "Like arrows in the hands of a warrior are sons born in one's youth. Blessed is the man whose quiver is full of them. They shall not be put to shame when they contend with their enemies in the gate." In his presentation, Phillips shows how the exponential multiplication of eight children each begetting eight children of their own would change what he sees as a godless country, where having perhaps two or three children has become the norm.
"Our age is defined by warfare against the Christian family," he says. "For our children to be mighty in the land, we must embrace a long-term vision of victory."
Quiverfull is a radical branch of the Christian Patriarchy movement, itself part of fundamentalist evangelicalism, and the nuances of observance make it tricky to estimate how many people in America adhere to its beliefs. What is certain is that thousands of families are withdrawing from the world, educating their children at home and living according to a literal interpretation of the Bible that stresses absolute submission to male authority.
"There's a lot of fear among evangelicals right now," says Garrison. "The more fearful evangelicals become, the more they retreat and start home schooling, and that is where they're going to encounter Quiverfull ideals.
"Families are taught that getting into powerful institutions is part of their dominion mandate. They get internships at state level, get involved in political campaigns and in the justice system. That's the whole point of having all these sons: to have an influence on policy and reclaim the country for God."
Patrick Henry College in Virginia, the headquarters of the conservative Christian Home School Legal Defence Association, sent more interns to the George W Bush White House than any other institution. Republican presidential front-runner Rick Perry has close ties to evangelical group Vision Forum through multi-millionaire campaign contributor Jim Leininger.
Lewis Wells has been writing about the movement ever since his fiancee, who came from a hardline Christian Reconstructionist family, abruptly broke off their engagement at her father's decree.
His website, Commandments Of Men, has become a hub for fundamentalists suffering a crisis of faith or looking for a way out. He says: "The women I deal with – and I hear from new people practically every day – their education is how to be a submissive wife and mother. They want to leave but they don't know how. A lot of the girls resort to self-injury, cutting themselves, to deal with the hell that they live in."
A TV reality show version of Christian Patriarchy can be seen in 19 Kids And Counting, starring Jim-Bob Duggar, his wife Michelle and their identically dressed, beatifically smiling brood: Joshua, Jana, John, Jill, Jessa, Jinger, Joseph… and so on.
Wells says. "They hook people with the perfect family portrait, talk about God, wave an American flag or two and otherwise intelligent people take the bait."
This was, essentially, what happened to Libby Anne, whose parents were ordinary evangelicals until they joined a community of Christians educating their children at home. Anne's mother had been a feminist at university and planned to return to work, but when a friend gave her a book by Debi Pearl, Created To Be His Helpmeet, her beliefs changed radically. Through their No Greater Joy Ministry, Pearl and her husband, Michael, preach that a woman's only godly role is to produce and raise children.
"The babies just kept coming," says Anne, who uses an assumed name to protect her 12 siblings. "My parents always wanted to have a big family, maybe four, five or so, but they never stopped, partly because of this belief that they were raising up an army for Christ. They told us they were training us to go out and convert others."
While being homeschooled, Anne learned that feminism is evil, that most people calling themselves Christians have been corrupted by worldly temptations and was taught that science supports the belief that God created the Earth in six days, around 6000 years ago.
Though she says she had a happy, busy childhood, her parents raised her to believe that the world was a scary, dangerous place.
"They talked about the possibility of a second American revolution. They saw a future when the government would put people in jail for home schooling and eventually just for being Christians." One day, her father took the kids to the home armoury and told them: "If need be, the resistance starts here."
As the eldest daughter, Anne became her mother's right hand, feeding, bathing, clothing, teaching and even disciplining her younger siblings. Another Debi Pearl book, To Train Up A Child, teaches that children should be spanked from the age of six months, to instil absolute discipline. The family rule was that Anne could punish those siblings who were at least five years younger than her.
In fundamentalist households, fathers have absolute authority, derived from the Bible, specifically Ephesians 5, 22-24: "Wives, submit yourselves to your own husbands as you do to the Lord. For the husband is the head of the wife as Christ is the head of the church." This may work for some families, but it can also lead to abuse. Garrison's husband was blind, unable to be the sole bread-winner, and beat and emotionally bullied the children.
"I started seeing my kids completely break down," Garrison says. "I recognised how abusive my husband had become as a result of this patriarchal teaching, which gave sanction to some of his worst tendencies. I had to step in and protect my kids because I didn't want to see them getting hurt."
One child attempted suicide. When, during a brief separation, Garrison's husband sent her a list of the ways in which she had been disobedient, she filed for divorce and won custody of all seven children. She now calls herself an atheist.
Garrison has collected scores of similar stories at her website, No Longer Quivering. The testimony of families who successfully pass on their beliefs is harder to come by. The Sunday Herald requested interviews with Vision Forum and No Greater Joy Ministries but received no response.
Joe Sands, one of seven children, was raised an Independent Fundamental Baptist. Despite doubts and private heresies – including listening to rock music and occasionally drinking beer – he stayed with the church until he and his wife, Kristine, had six children of their own.
But then, two years ago, a whooping cough epidemic swept through the congregation in Normandale, Minnesota, almost killing his son, Jack. "This movement is very paranoid about anything 'worldly,' which is a very relative term, so they don't trust doctors and don't believe in getting vaccinated," he says. His crisis of faith began in earnest.
The obvious flaw in the 200 Year Plan is it relies on children swallowing the belief system and replicating its rigid authoritarian structure in their own families. Sands claims that, in practice, few hardline patriarchal households stay together.
He says: "I explain it like the wet soap bar. You're going to lose the wet soap bar, so you press harder and it squirts out of your hand. I watched families break apart all around me as I was growing up. The sad part is that once the kids leave, the parents who are so indoctrinated reject them. My mother immediately rejected me when I left."
Anne still has a relationship of sorts with her parents, but it has taken years to rebuild, since the day she came home from university and questioned everything they stood for. "Nothing that I can do or achieve in life – not my stable and happy marriage, not my child, not school or work – will ever please them," she says.
However, thanks to the education they gave her, she is well-equipped to handle the world on her own, unlike other Quiverfull refugees who have spent their entire fertile lives pregnant and raising children.
"They don't have any money, any training, any idea how to navigate the world without their husband. It's heart-breaking," says Wells.
For now, the informal support network run by Garrison is the only dedicated resource they have.
"It can be really sad and overwhelming reading their stories," she says. "Sometimes I just shut my computer off and walk away and think: 'I can't deal with this.'
"The one thing that is encouraging is these are very tough women. When it comes time to get their life out of the pit, they'll do it."