By LEE BOWMAN and THOMAS HARGROVE

Penny Callonas: Penny Callonas of Memphis said she needed to seek help after the loss of her son to SIDS. "I could not be a good mom or wife," she said reflecting on the difficult time. (SHNS photo by Karen Pulfer Focht / The Commercial Appeal)Victoria LaBarbera fell asleep cuddling her baby one June evening in her Broward County, Fla., home. Brooklyn Ruth LaBarbera never woke up. She was 6 months old.

"I woke up, she'd been on my chest for like half an hour, and she was unresponsive and my world came crashing down," LaBarbera said. "The medics came and took her away and they wouldn't let me ride with her. When I got to the hospital, I waited for what seemed like eternity before a doctor came out and told me we don't expect your child to make it, she's been without oxygen for at least 12 minutes."

Brooklyn stayed on a ventilator for 22 hours, but never revived and was declared brain dead later that day in 2005. "I went into what seemed like a coma. I was unable to speak or move or function," LaBarbera said.

"The medical examiner's people went from story to story about what had happened to her, but kept telling me it wasn't SIDS. Six months after she died, I got a death certificate that said SIDS, with a contributing factor of pneumonia. When they don't know what it is, it's SIDS. I had no choice but to accept that, but they really have no idea what happened to her, I'm convinced."

For thousands of parents of healthy babies who die suddenly and unexpectedly each year, lingering doubt and confusion over how their child died exacerbate the pain of losing an infant.

Uncertainty fuels the nagging worry that they might have done something -- or not done something -- that could have changed what happened.

Most of the time, in most parts of the country, the official explanation for the sudden death of a baby up to 1 year old is SIDS -- Sudden Infant Death Syndrome -- a diagnosis reported to the federal Centers for Disease Control and Prevention for more than 2,200 baby deaths in 2004, the most recent year for which complete data is available.

The grave of Devon Callonas: Devon "Trace" Callonas born to Penny and Jason Callonas on May 22, 2002, died from SIDS on July 30, 2002. (SHNS photo by Karen Pulfer Focht / The Commercial Appeal)But in nearly half of sudden infant deaths in the United States, a Scripps Howard News Service review found, coroners and medical examiners are either finding evidence that something specific caused a child to stop breathing or that the death was unexplained, but did not meet criteria to be classified a SIDS death.

SIDS itself is a diagnosis that is supposed to be reached only when all other medical explanations have been ruled out -- when an autopsy, a death scene investigation and a review of medical history reveal no apparent cause of death. It is a medical mystery that's evaded any simple explanation despite more than a half-century of research.

Most experts believe there are multiple causes for SIDS, but there's little conclusive evidence of why some infants -- many asleep, but others wide awake -- simply stop breathing and die.

Many of the dozens of parents interviewed by Scripps about the unexplained death of their babies say they take some solace from being told SIDS was to blame -- that despite their desperate calls to 911, their attempts at infant CPR, sometimes the heart-wrenching decision to remove a brain-dead baby from life support, there was nothing they could have done.

Others whose infants weren't added to the tragic toll of SIDS victims express confusion, hurt and regret at the exclusion, of being told that the baby's sleep environment contributed to the death, or that some unexpected finding in an autopsy didn't fit a classic SIDS case.

"The medical investigators, even my pediatrician, told me that the finding of SIDS means you didn't do anything wrong. But it also means it can happen to any baby, even one that's completely healthy, like my son," said Rachel Yerbich, whose son, Benjamin Allen, died from SIDS on Sept. 26, 2006, at 21 weeks of age in Granite Falls, Minn. She and her family now live in Montana.

"He was a perfect baby, he never cried, but he liked to be held. After they unhooked him from all the tubes and things in the emergency room, I held him from like 6 p.m. until 1 or 2 in the morning, as my husband and family members came in.

Rachel and Jesse Yerbich: Rachel and Jesse Yerbich had four-and-a-half months with their son, Benjamin Allen, in their home in Granite Falls, Minn. "It was hard to answer the investigators' questions, but looking back I understand why they have to ask them. It took a couple of weeks for the autopsy results and I kept calling to find out what had happened. I got a copy of the autopsy report so I could physically look at the findings and see that I didn't do anything wrong," said Yerbich.

SIDS "is a very, very comforting diagnosis for a parent who is grieving," said Dr. Henry Krous, a noted child pathologist and director of the San Diego Sudden Infant Death Syndrome Research Project. "A diagnosis of SIDS states that the caregiver was not responsible."

Krous and other experts say the impact of the death of a baby on a family, on a couple, is often devastating. Blame, guilt, anger take hold and divorce is common. Depression and even parental suicide sometimes follow. Even families that stay together often move to new homes, new towns. They often fear having more children, and if they do, spend endless sleepless nights keeping vigil over the new baby.

What people think

"There is a stigma. You tell people you're a SIDS parent and you see that look of questioning in their eyes," said Suzette Gripp, whose daughter, Sheyenne, died in Memphis, Tenn., in 1974. She has devoted more than three decades to researching and educating parents about sudden infant death, even conducting her own research on possible causes using a seven-page questionnaire answered by several hundred parents. "I had hoped to know in my lifetime why my daughter died, but I wonder if I will," said Gripp, now 52.

Parents and researchers fought for official recognition of SIDS during the 1970s, but now some parents say SIDS has become a hollow explanation.

"You feel SIDS, even though it is an answer, it isn't really an answer. It's comforting and not comforting at the same time,'' said Sarah Lucero of Keller, Texas, whose son, Grant, died in 2004, 10 days shy of his first birthday.

"We went through the autopsy and all these tests, and I went along because I kept thinking they'd be able to tell me why a perfectly healthy child passed away in his sleep," said Brandy Hazel, a Lubbock, Texas, mother of three whose son, Cole, died in July 2006, just shy of 3 months old.

"When they told me it was SIDS, I called the coroner up and said there must be a mistake. Then they sat me down with the autopsy report and showed me there was absolutely no reason for him to have passed away. They can't find a reason, so it's SIDS."

A diagnosis of uncertainty

Suzette Gripp: Suzette Gripp was 18 and living in Memphis, Tenn., when her daughter, Sheyenne, died at three-and-a-half months of age in 1974. She was in shock and grief, but like many SIDS parents, but dedicated her life to solving the mystery of SIDS."They simply do not know why my daughter died. I put her to bed and she never woke up,'' said April Poole of Huntsburg, Ohio, whose daughter, Sommer, died from SIDS in 2005 at 10 weeks of age.

"In my opinion, whether it's called 'unknown' or SIDS is one in the same to me. We don't know what causes SIDS. Not that her loss would hurt any less if we knew why, but we would have something," said Poole, who like many SIDS parents has set up a foundation to help support research and awareness into infant death.

Gripp, the Tennessee mom who's been battling to solve SIDS, says to her, no theories of what causes the syndrome nor any efforts to reduce risks can be given credibility "until we can be sure of the numbers across the country.

"The numbers are so skewed, so that while SIDS seemed to be declining, it may not have been. Until we have actual numbers of actual SIDS deaths, and a good national database of the death investigations, the autopsies, the tissue samples, the DNA, we're not doing all we can to give babies a chance to grow up."