"My husband and I went to the hospital thinking this was going to be one of the greatest moments of our lives and it turned out to be nearly fatal," Miranda Klassen tells PEOPLE

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When Miranda Klassen’s trouble-free first pregnancy ended in an almost fatal delivery, she woke up from a medically induced coma with a newborn son and very few answers.

Now, the San Diego, California woman has dedicated her life to supporting families that have been affected by the rare birth complication that almost killed her – and unraveling the medical mystery that surrounds it.

“My husband and I went to the hospital thinking this was going to be one of the greatest moments of our lives, and it turned out to be nearly fatal and completely life-changing for both of us,” Klassen tells PEOPLE of that fateful day in 2008.

While in labor, the San Diego, California, woman suffered an amniotic fluid embolism, which is an unpreventable and often-fatal complication of pregnancy that occurs when amniotic fluid enters a mother’s blood stream and triggers an allergic-like reaction.

“The first phase is cardiorespiratory collapse, where your heart and your lungs stop,” Klassen, 39, explains. “If you live through that, the next phase is massive hemorrhaging – your blood cannot coagulate and you bleed from every orifice.”

While AFEs are extremely rare – occurring in approximately one out of every 40,000 births in North America – they are among the leading causes of maternal death in the United States. Estimated fatality rates vary widely – from 80 to 40 percent among mothers and 65 percent among infants still in the womb during an AFE.

Those that do survive often face permanent neurological damage. “The majority of women who suffer an AFE die, while those that survive are often left in a persistent vegetative state,” Klassen says.

After waking up from two days in a medically induced coma, Klassen learned that she had survived because two people on her medical team at Scripps Memorial Hospital Encinitas recognized her symptoms early on. She also learned that many women with AFE are not so lucky.

Just months after leaving the hospital, Klassen started the Amniotic Fluid Embolism Foundation – a non-profit patient advocacy organization that supports mothers and families affected by AFEs.

To date, the AFE Foundation has helped more than 25 survivors go on to safely have another child. The foundation has also established the world’s largest registry of AFE cases to advance medical research.

A Life Forever Changed

“My husband and I were fortunate in that we were able to get pregnant really easily,” Klassen says. “Everything about the pregnancy was uncomplicated. We found out we were having a boy, and I had always had visions of three little boys running around my house.”

In April 2008, Klassen went into labor. After several hours, nurses noticed that the baby’s heart rate was decreasing and an emergency C-section was ordered.

“Before they got the gurney out of the door, I started to have a seizure,” Klassen says. “I was convulsing and my eyes were rolling into the back of my head and my heart stopped.”

Klassen’s husband, Bryce, was ordered to leave the room. A nurse told him soon after that his son had been delivered and resuscitated while doctors continued to work on his wife.

“Forty-five minutes later, my OBGYN came out covered in blood and completely shaken and told my husband that the he believed I was suffering from a very rare complication that was fatal,” she shares.

After her heart and lungs failed, Klassen began hemorrhaging. She was then placed in a medically induced coma so that she could breathe with the aid of a machine.

“There was a team of about 20 different doctors and clinicians working on me, and they drained the hospital’s entire blood bank,” she explains. “The doctors told my family they could not guarantee that I would survive the night and added that if I did, they were fairly certain I would not be the same person I was when I checked into the hospital.”

While Klassen remained in a coma for two days, her family had no idea if she would ever meet her newborn son. When she woke up, she had no recollection of what had occurred – the last thing she remembered was checking into the hospital days earlier.

“[My] first reaction when I woke up from the coma was trying to wrap my head around what had happened,” Klassen tells PEOPLE. “And the second was being shocked that this was all part of the norm.”

A Newfound Purpose

Klassen was released from the hospital eight days later with her son and a host of medical complications.

“I had longterm heart and kidney damage,” she says. “I had several procedures done to stop the bleeding, and I won’t be able to have anymore children. I had very little short-term memory, and I asked questions over and over again.”

Still, the new mother found the energy to search for more information about the rare complication that had almost taken her life – and was shocked when she found very little research.

“I told my husband, ‘Honey, this is crazy. There’s no research, there’s no organization, I’m going to start one,’ ” Klassen recalls.

Five months later, she returned to her full-time job in corporate finance and spent her nights developing her foundation. Her husband also found a new calling – going back to work to become an intensive care unit nurse so that he could work alongside the team that saved his wife’s life.

“Our son went to daycare and after I would put him to bed, I would get on the computer and work until midnight,” she says. “I found researchers and experts and emailed them saying, ‘How do we stop this? How do we prevent this? This is horrific, women are dying and no one has heard of it.’ ”

One of those experts, Dr. Gary Dildy, a Houston-based obstetrician-gynecologist, now serves as the medical advisory board chair for the AFE Foundation and works closely with Klassen on advocacy and research.

“Miranda was very passionate about trying to do something to support people and their families who have had to contend with this rare and poorly understood condition,” Dildy tells PEOPLE. “So we started collecting medical records and interviews and getting together as much information as possible.”

This research led to the creation of the AFE Registry at Baylor College of Medicine – now the world’s largest research registry for AFE. Dr. Dildy tells PEOPLE this research “stands to be the best hope for unraveling the mystery of AFE, the most feared complication of childbirth.”

A Hope for Survivors

While Klassen collaborated with researchers in the hopes of one day being able to prevent women from dying of AFE, she also dedicated herself to helping the families of those who had gone through the horrifying experience.

“We work with the husbands who now have motherless children, having lost the loves of their lives on the very day that their first-born was brought into the world,” Klassen says. “It’s the hardest part of what I do, but it’s also the part that means the most to me.”

In January 2015, Klassen quit her job in finance to run the foundation full time, “making minimum wage and loving every minute of it,” she adds.

The foundation now offers support groups for grieving fathers and families, as well as parents grieving the loss of an infant. It also offers guides on managing medical expenses, finding psychological support and connecting with other survivors and families.

“It’s very isolating when you wake up from a coma and are told, ‘Oh you’re very lucky you’re alive, it’s such a miracle,’ ” Klassen says. “To be able to pair up a mother who lost her daughter in childbirth with another mother who s walking the same path is so important and so vital to their healing.”

Thanks to the network Klassen created, many AFE survivors have gained the support they need to have another child.

After surviving an AFE in the 2008 delivery of her 28-week-old son, Amy De Simone of Atlanta, Georgia, dreamed of having more children, but she was terrified to try.

“I went around and interviewed different OBGYNs and tried to get collective feedback on whether or not it would be something we could pursue,” De Simone, 39, tells PEOPLE. “One man said he would be scared to be my doctor.”

However, she found the hope she so desperately needed in an AFE Foundation support group dedicated to women who have gone on to have successful deliveries.

“If I had not connected with Miranda and I had not found this group, I’m not sure we could ve ever gotten through that mental road block of how scary it was,” she reflects.

Now, the mother of sons Aiden, 7, and Liam, 3, serves as board chair for the AFE Foundation and oversees many of the foundation’s outreach, education and support programs.

“My ultimate hope is that we will solve AFE because no one should have to go through it,” De Simone says. “In the meantime, we just want to be there to support these families so that no one has to be alone.”

Klassen and her staff work tirelessly to support those who have been affected by AFE, making personal connections with families across the country.

Klassen visited the family of a woman in Texas who had died during the birth of her eight child. After learning that Klassen had lived through the same complication that took his mother’s life, one of the woman’s younger sons came up and asked her, “Why did you live and my mother died?”

“I had huge tears,” Klassen says of her conversation with the young boy. “I scooped him up and I said, ‘I’m sorry. I don’t know why, but I promise you that for the rest of my life I will work to get you that answer.’ ”