Three months after her baby girl’s death, Andrea LaVigne of Grafton says she still doesn’t know what caused her one-month-old’s heart to stop while they lay in bed together, a blanket half covering the child’s face.

Because the infant was born drug-dependent and LaVigne had been under state watch for potential abuse or neglect, Aliana’s death raised public concerns that social workers had once again failed to protect a child in a troubled home -- just as they failed Jeremiah Oliver, the five-year-old Fitchburg boy who was found dead the same month.

Yet details of Aliana’s death, child advocates suggest, may also point to a cause that is less nefarious than abuse, but just as devastating and perhaps preventable: Sudden Unexpected Infant Death, the leading cause of death in children between one month and 12 months nationally and in Massachusetts.

If Aliana’s death is found to be a case of SUID, which often occurs when the child is in bed or sleeping, she would be one of at least two dozen children under state watch who died suddenly and unexpectedly between 2010 and 2012, according to the state Office of the Child Advocate.

Indeed, children in homes supervised by state social workers die suddenly and unexpectedly at least twice the rate of infants statewide, according to an analysis of the most recent available data by the New England Center for Investigative Reporting. That suggests to child welfare advocates that more should be done to educate caretakers of some of the state’s most vulnerable children about how to minimize the risk of sudden death.

An investigation into Aliana’s death is still pending. But LaVigne detailed several circumstances about her newborn’s death that health officials associate with greater risk of SUID: bed sharing, side-sleeping, bed-covers on the baby’s face, and even prenatal exposure to drugs. LaVigne, 35, told the New England Center for Investigative Reporting that she never meant to put her baby in danger – but now is left to wonder what caused her devastating loss.

She wondered whether the hospital is at fault for not adequately treating Aliana, who was born with the medication Klonopin in her blood because Andrea LaVigne took it during pregnancy to prevent seizures. She said the baby was in bed with her, but that she left enough space to breath. “A lot of people told me they slept with their babies all the time. If this was SIDS, it is an unexplained thing,” she said last week, using the acronym for Sudden Infant Death Syndrome, the term used for SUID deaths for which there is no clear cause.

But Jetta Bernier, head of the nonprofit advocacy group Massachusetts Citizens for Children, said that when she first heard of Aliana’s death, she immediately wondered if it was sleep-related. She worries not enough is done to educate parents -- both in and out of the social services system -- about risks of sudden infant death.

“There needs to be more publicity because these are obviously preventable deaths,” Bernier said. Safe-sleep campaigns appear to have reduced the incidence of sudden infant death nationwide from 1.6 deaths per 1,000 infants in 1990 to 0.94 in 1998 following a national “back-to-sleep” campaign promoting placement of infants on their backs at bed time.

But the number of these deaths has remained stable since 1998, in part because health specialists now realize that many previously unexplained deaths were actually due to sleep-related causes like accidental suffocation and entrapment. Today, more than 3,000 babies die suddenly and unexpectedly nationwide annually.

“In Massachusetts we lose the equivalent of one to two classrooms of preschool students each year to sudden unexpected infant death, and that almost all those infants died in unsafe sleep positions,’’ said Gail Garinger, head of the state Office of the Child Advocate.

Garinger urges the state to invest more in protecting all children from SUID, but has long been concerned that the risk may be higher for children in families that are overseen by state social workers. Almost all of the infants under DCF supervision who died between 2010 and 2012 did so in what are considered “unsafe sleep” settings such as sleeping with an adult or on their bellies, according to the Office of the Child Advocate.

That doesn’t mean the sleep settings definitively caused death, but statistics show that SUID strikes infants more often in unsafe sleep situations. So health advocates urge parents to put children to bed alone on a firm mattress, on their backs, without pillows or blankets.

The latest state data points to a disproportionate number of deaths among agency-supervised children. Of the 72 Massachusetts infants who died of SUID in 2010 and 2011, at least 20 – nearly 30 percent – had recently been under state social service care, according to the latest available data provided by the state Department of Public Health and the Office of the Child Advocate.

But DCF-supervised infants constitute less than 10 percent of the total Massachusetts population of children under the age of 1, suggesting that children in these homes are at double the risk of sudden and unexpected infant death. Preliminary numbers show the number of children in DCF-supervised homes who suffered sleep-related deaths fell from 12 in 2011 to 8 in 2012, but the total could change as more autopsy results are reported and more information comes in.

The Massachusetts numbers match new evidence nationally that children with histories of abuse and neglect among other issues are more likely to die of SIDS and other sleep-related deaths. A recent report in the Journal of Pediatrics found that California children who had a reported history of abuse or neglect were three times more likely to suffer sudden infant death than in the general infant population. Lead author Emily Putnam-Hornstein said the disparity is likely due to the fact that high-risk families are not adopting safe-sleep practices or that children are endangered by their parents’ issues, like substance abuse.

“The public pays attention when there is a sensational headline because a child dies from abuse,” said Emily Putnam-Hornstein, an assistant professor at the University of Southern California, in Los Angeles, and lead author of the California study. “We don’t pay enough attention to many other types of death that are more common for this population.”

When little Aliana LaVigne died on April 11, public attention quickly turned to whether DCF had done enough to protect her. Grafton police had faxed a warning about the safety of Aliana’s home to DCF -- they had visited the home multiple times in response to reports that Aliana was crying -- but a social worker misplaced it until after the baby’s death. So far there have been no criminal charges and an autopsy report is still pending from the Chief Medical Examiner. LaVigne maintains her baby died in her sleep.

Despite the intense focus on the failings of child welfare agencies, efforts to study and prevent child fatalities in Massachusetts have faltered. In 2000, the state Legislature created a child fatality review program headed by the state Chief Medical Examiner, and aided by teams based in the 11 District Attorneys’ offices.

The program is expected to examine child fatalities statewide, including those where SUID is suspected, and recommend ways to prevent future tragedies. But the study teams do not receive state funding and some struggle to prepare their reviews with volunteers and unpaid interns. Indeed, the state has not produced a mandated annual report since 2011, and that one was for child deaths between 2006 and 2008. Massachusetts Child Advocate Garinger said she has repeatedly pushed the state to devote resources to the child fatality teams so they can better understand and prevent child deaths.

“It is time for Massachusetts to realize the value of the child fatality review program and to send resources to both the state and local teams,’’ she said. Terrel Harris a spokesman for the state’s chief medical examiner says a new report is “under review,” but said the Department of Public Health is in charge of its release. A spokeswoman for that agency on Friday could give no details about when the next report will be made public. Harris confirmed the fatality review program lacks resources. “The committee has no staff, has no funding, has no nothing,’’ Harris said.

Officials from the Massachusetts DCF said they do not analyze whether at-risk children die more often in unsafe sleeping situations compared with the general population. However, they said that such a disparity is likely because many challenges faced by troubled families – including poverty, cramped housing and substance abuse – are linked to increased risks of all sleep-related infant deaths.

The agency has increased efforts to educate families about safe-sleep habits over the past two years, said Amy Kershaw, DCF’s assistant commissioner for policy and practice innovations. In May, the state launched a “welcome baby” initiative in which state social workers provide guidance to new parents under their supervision about safe sleep and other health efforts. However, Kershaw added that the state can not force parents to change habits associated with sleep-related deaths. “We are working with a highly risky population,’’ Kershaw said.

“Co-sleeping and being poor and some of these risk factors are not necessarily illegal.” Officials in some states have been so troubled by what they consider preventable deaths that they have tried to find ways to criminally prosecute parents whose infants die in situations considered risky. In Wisconsin, for example, lawmakers filed a bill last year to make it illegal to sleep with an infant while intoxicated.

But most health advocates argue that it’s far more helpful to educate parents and caretakers about ways to protect their babies than punish them. For instance, Putnam-Hornstein of USC said social workers need to tailor their message to the realities of lives in troubled families. “A simple but important message may be that if you are going to sleep with your infant, make sure you are sober,” she said.

Some child welfare advocates worry that even well-intentioned public education campaigns can hurt more than help by giving parents conflicting information. The La Leche League International, a breastfeeding support group, believes that some “safe sleep” messages don’t recognize the realities of childrearing, particularly for women who breastfeed. The nonprofit is coming out with a book this summer advising breastfeeding mothers to sleep with their babies if they avoid other risk factors like smoking, abusing drugs or alcohol, or allowing their baby to overheat.

Aliana LaVigne is one of at least three infants under the watch of DCF who died this spring – and in each sad case there is some evidence that the children died of SUID. In April, 16-day-old Bailey Irish died in Fitchburg. Her mother Charis declined repeated requests for an interview but recently filed a petition on the website urging the state to return her oldest son, Conlan, who was taken away after Bailey’s death.

In the petition, Irish attributed Bailey’s death to SIDS, saying she put her newborn to sleep and 50 minutes later the baby stopped breathing. DCF, which said the Irishes have been receiving social services since 2012, declined to comment on the petition.

In May, 10-week-old Grace Lynne Hooks was found unconscious by her father Melvin Hooks in their small room in a Weymouth homeless shelter. The grieving Hooks, who has tattooed his deceased daughter’s name on his neck, said state officials told his girlfriend that Grace died of SIDS, but he is awaiting confirmation from the medical examiner.

Hooks said he had been living with Grace, his girlfriend and teenage son in the shelter for more than a year before she died. DCF officials confirm that they had recently opened an investigation of the family before Grace’s death. Hooks said he was aware of safe-sleep guidelines and followed them. Both he and his girlfriend smoke (which is considered a risk to infants), but never around the baby, he said, adding that Grace had been placed on her back to sleep and rolled onto her side before she died.

David Traub, a spokesman for Norfolk District Attorney Michael W. Morrissey, said detectives did not find signs of foul play and are awaiting the final autopsy report. Like anyone grieving the sudden, unexpected loss of an infant, Hooks, who found his daughter’s body, wondered if there was something he could have done differently: “I don’t understand how a baby can be perfectly healthy and pass away."