Warrington, Pennsylvania (CNN) Mary and Greg Pellegrino are thinking about having a second child, but they're not considering the factors couples usually do, such as whether they can afford it or whether they have enough space in their house.

Their decision rests squarely on this question: Will Mary die?

She almost did the first time.

Mary Pellegrino, now 35, had a severe form of preeclampsia. The hallmark of the disease is high blood pressure, and it affects about 3% to 5% of pregnancies in the United States. There's no cure, and so doctors deliver the baby, even if premature, to try to save the mother's life.

Since Pellegrino had it once, she's at an especially high risk of getting it again. Although her doctors can give her ballpark figures, they can't say exactly how likely she is to have a recurrence or, if she does, whether it will be just as severe.

So every day, the choice looms over them. They want their 3-year-old son, Bennett, to have a sibling, but they don't want to risk his mother's life.

"It's a gamble. A big, big gamble," Pellegrino said.

Photos: Preeclampsia survivors on the risk of having another baby Mary Pellegrino gave birth to Bennett 15 weeks early. He weighed 1 pound, 2 ounces. She was in the intensive care unit after suffering a complication of preeclampsia called HELLP, which includes liver damage. Hide Caption 1 of 12 Photos: Preeclampsia survivors on the risk of having another baby Bennett is now 3 years old and has cerebral palsy and cancer. He also had liver cancer, a complication of his treatment in the neonatal intensive care unit. His parents would like to have another child but worry about Pellegrino's health and the possibility of another child with special needs. Hide Caption 2 of 12 Photos: Preeclampsia survivors on the risk of having another baby Eleni Tsigas was diagnosed with preeclampsia when she was 11 weeks from her due date. Her daughter, Nikonia Evangelia, was stillborn. Hide Caption 3 of 12 Photos: Preeclampsia survivors on the risk of having another baby Tsigas and husband Demetri went on to have two more children, Jordan and Jonathan, who are today healthy teenagers. Hide Caption 4 of 12 Photos: Preeclampsia survivors on the risk of having another baby As with many women, Laura Bocko's preeclampsia was misdiagnosed for several weeks even though she had many of the symptoms. Her son, John David, was born 12 weeks early. He was stillborn. Hide Caption 5 of 12 Photos: Preeclampsia survivors on the risk of having another baby After hesitating to get pregnant again, Bocko -- here with husband John -- got the OK from her doctor and started trying. Now 42, she's been unable to get pregnant and has decided not to undergo fertility treatments. Hide Caption 6 of 12 Photos: Preeclampsia survivors on the risk of having another baby Caroline Dunn and Syed Ali – Caroline Dunn delivered daughter Camille Cosette Ali 16 weeks early because of preeclampsia. She was stillborn. Dunn was headed toward kidney and liver failure. Hide Caption 7 of 12 Photos: Preeclampsia survivors on the risk of having another baby Dunn and Syed Ali decided against another pregnancy. "We lost a baby, and we almost lost me. We couldn't put another baby or me through that again," she said. They now have twin daughters Darcy Camille and Sophie Cosette with surrogate Angela Zarate. Hide Caption 8 of 12 Photos: Preeclampsia survivors on the risk of having another baby Dani Rose Voelker was born full-term and healthy. When she was a week old, her mother was diagnosed with preeclampsia and HELLP. Hide Caption 9 of 12 Photos: Preeclampsia survivors on the risk of having another baby Jennifer and Jake Voelker are now considering having another baby or possibly adopting. "My husband and I are in a quandary," Jennifer Voelker said. "I'm more inclined to say yes, and he's more inclined to say no. I only remember bits of it, but he lived every minute." Hide Caption 10 of 12 Photos: Preeclampsia survivors on the risk of having another baby Wyatt Kellen Simpson was born healthy and full-term in 2015. Mom Rachel's kidneys and liver failed in delivery, and she spent three days in the intensive care unit with preeclampsia and HELLP. Hide Caption 11 of 12 Photos: Preeclampsia survivors on the risk of having another baby Wyatt will be 2 years old in June. Rachel Simpson -- here with husband Colin -- now has a heart condition and post-traumatic stress disorder after her ordeal. She's been trying to get pregnant again. "We are hopeful and hesitant at the same time," she said. Hide Caption 12 of 12

Preeclampsia has been recognized since ancient times, but researchers still haven't figured out exactly what causes it and why it strikes otherwise-healthy women like Pellegrino.

"Preeclampsia is a mystery disease," said Dr. Michael Paidas, professor and vice chairman of obstetrics at Yale School of Medicine.

About 200,000 women a year in the United States are diagnosed with preeclampsia. Of those, about 40,000 have severe cases, according to Eleni Tsigas, executive director of the Preeclampsia Foundation.

Globally, the Preeclampsia Foundation states the number of women developing the condition each year is ten million, with an estimated 76,000 deaths from preeclampsia and related hypertensive disorders.

"It's life-threatening to mom and baby or both," said Tsigas, who had the disease. "It's an incredibly difficult decision about whether to have another child."

A sudden shock after a perfect pregnancy

When I visited Mary and Greg Pellegrino at their home in Warrington, Pennsylvania, I felt an instant kinship.

Like her, I had suffered from severe preeclampsia.

We shared a feeling. It isn't anxiety, exactly, but a feeling of looking back at a traumatic event and thinking "What the ... ?"

Like Pellegrino, my first pregnancy was textbook perfect until all hell broke loose. My blood pressure, normally way below normal, shot up to 225/125. My kidneys started to fail. I was unable to move my arms or legs or open my eyes due to magnesium sulfate, the highly toxic medicine used to treat the disease. Then, when I could open my eyes, all I could see was red spots due to retinal damage from the extremely high blood pressure.

Doctors had to deliver our daughter seven weeks early. She weighed 3 pounds. At that gestational age, she should have been considerably larger, but the disease compromised the nutrition she received inside me.

Pellegrino had preeclampsia much earlier in her pregnancy than I did and was even sicker.

She was 15 weeks from her due date when she was diagnosed. To try to stop the disease, doctors had to deliver Bennett. He weighed 1 pound, 2 ounces.

While Bennett struggled in the neonatal intensive care unit, Pellegrino fought for her life in the adult ICU. She developed a complication of preeclampsia called HELLP, which includes liver damage.

For the Pellegrinos, the road to parenthood was life-threatening and terrifying.

Do they dare walk down it again?

A worried father

Studies show that a woman who had severe preeclampsia in her first pregnancy, like Pellegrino, has about a 20 to 40 percent chance of getting it again. If preeclampsia does strike twice, there's an 80% chance it will be less severe, according to Dr. Douglas Woelkers, professor of maternal-fetal medicine at the University of California, San Diego, School of Medicine

Although mortality rates from preeclampsia are quite high in developing countries, death is relatively rare in the United States. According to a study by the Centers for Disease Control and Prevention, 317 women died from hypertension-related complications of pregnancy in the US from 2006 to 2010.

Pellegrino is much more willing than her husband to take those odds. She knows that she could take a low-dose aspirin during her pregnancy, which has been shown to decrease the risk of preeclampsia by 24%. She knows that high-risk doctors will be ready and waiting to treat her if anything were to go wrong.

"I know how much I love my brother, and I know how much Greg loves his brothers," Pellegrino said. "Siblings have a bond and a relationship like no other."

She wants that for Bennett, who has cerebral palsy and seizures.

"I have a son who's going to be here after I leave this world," Pellegrino said. "I know that Bennett would always have somebody on his side, no matter what."

Greg Pellegrino would also love a brother or sister for Bennett, but his calculus is different than his wife's.

"My biggest thing is, I can't lose her," he said. "I can't imagine life without Mary, even if it meant having another child. I know that's something we both definitely would want, but I can't see life without her. I think it's just too much of a risk."

Preeclampsia experts say it's often the fathers who are the least willing to roll the dice.

"Women with preeclampsia are so sick from brain swelling that they don't remember very much of what happened. They just remember little snippets. The husband remembers every single moment," said Dr. Thomas Easterling, professor of maternal and fetal medicine at the University of Washington School of Medicine.

"I've seen fathers cry at the thought of their wives going through that again and losing them," Woelkers said. "I'm a father myself. I can understand the reluctance to lose her to some unknown force, to such a risk that's so poorly understood."

Pellegrino understands her husband's reluctance to have another baby.

"I see the look on his face when he talks about the fear of losing me," she said. "That's something that I would never want to have come true for him."

Greg too understands his wife's feelings.

"I know I'm very adamant about saying 'no, we're not going to go down that route of having another child,' but I don't think it's a closed chapter. I don't think it's the end. We don't know what the next couple of years are going to look like. The door is slightly still open on my end," he said.

In the Pellegrinos' garage sits a huge stash of baby equipment: a beautiful crib with sheets, a swing, a full set of Dr. Brown's bottles. There's so much, they can't even park the car there.

Greg wants to sell it all. Mary can't bear to part with it.

The baby stuff sits there, a symbol of their indecision.

"Greg and I are at an impasse," Pellegrino said.

Losing a baby to preeclampsia

No two cases of preeclampsia are exactly alike, and in the end, each family has to make its own decision.

According to an unpublished survey by the Preeclampsia Foundation, of 424 women who had severe preeclampsia, 326 said that experience influenced their decision to become pregnant again.

Of those 326, 28% said they decided not to get pregnant again, even though they did want another child. Another 14% said they were considering or had pursued adoption or surrogacy, two routes the Pellegrinos are thinking about but aren't sure they can afford.

Tsigas, the executive director of the Preeclampsia Foundation, thinks about the decision she and her husband had to make. Their first baby, Nikonia Evangelia, was 11 weeks early and stillborn because of preeclampsia.

Tsigas' kidneys shut down. She lost half her body's blood supply.

Over 200 mourners attended Nikonia's funeral in the freezing rain.

"As my wheelchair was pushed over the mud to the grave site of my firstborn, I realized that nothing in my life would ever, ever be as tormented and heartbreaking as burying my child. If there was anything magical and innocent left, it was gone," she wrote on the foundation's website

A year and a half later, in August 1999, Tsigas gave birth to a son. Preeclampsia did strike again, but it was much less severe and later in the pregnancy. Her son was born four weeks early and weighed 4 pounds, 10 ounces.

Two and a half years later, Tsigas had another son. This time, she didn't get preeclampsia, and he weighed 8 pounds.

My experience was very similar. Eighteen years ago, after the birth of our first baby, my husband and I decided to have a second child. The preeclampsia was much more mild, and she was born five weeks early and small for her gestational age but much bigger and healthier than her older sister. We went on to have two more children who were full-term.

A message from God

For families that decide to get pregnant after preeclampsia, Tsigas advises that they learn as much as they can about the disease and get a specialist who will monitor them sufficiently during pregnancy.

For Tsigas, having another child also required faith.

In her second pregnancy, she started bleeding early on. Her doctor said her levels of hCG, the pregnancy hormone, weren't rising fast enough.

"The doctor said, 'Don't get your heart set on this pregnancy working,' " she remembers. "I was devastated."

She wanted to go home and crawl into bed, but when she approached the highway exit for home, she drove past it.

Instead, she drove to Holy Trinity Greek Orthodox Church in Portland, Oregon, where her husband, the Rev. Demetri Tsigas, a priest, was helping lead the feast of the Epiphany service, celebrating Christ's baptism in the Jordan River.

"God spoke to me during that service. I don't think God speaks in words and language that we expect as humans. It was a metaphysical message but a very specific message: I knew it would be a boy, and we would name him Jordan, and he would be fine," she said.

"The message was as solid as the chair I'm sitting in right now," she added. "I left there with a total feeling of peace having overcome me. I walked out feeling transported."

Tsigas got back in her car to drive home. Another priest, her husband's colleague, tapped on her window. She rolled it down.

He told her how sorry he was to hear that the doctor had said they were about to lose their baby.

"I told him, 'No, it's OK. The baby is going to be OK. Everything is fine,' " she remembers.

And everything was. Tsigas went back to the doctor a few days later, and her hCG levels were normal.

Emotionally, it wasn't always an easy pregnancy, especially as she approached 29 weeks, the week her daughter was born and died.

"You gotta be on Xanax, but of course you can't be on Xanax," she said, laughing.

She bled early on in the pregnancy. Then, six weeks before her due date, she was diagnosed with preeclampsia. Again, Tsigas talked to God.

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"I said, 'You told me the baby would be OK.' God said, 'I didn't say it would be without difficulty. I just said it would be fine,' " she remembered.

Today, Jordan, 17, and his brother, Jonathan, 15, are healthy.

Although Tsigas' story has a happy ending, she understands why some couples would choose not to walk down such a potentially treacherous road again.

"The risk of something terrible happening again to most people is pretty small," she said. "But there's no crystal ball you can log into. There are no guarantees. You just have to make a decision and live with the consequences."