Despite a variety of clues, SIDS remains a mystery


John and Julie's son had grown and developed into a smiling, happy child over the three months since his birth. Premature, he had overcome his low birth weight. He was even sleeping for four-hour stretches at night. One morning, Julie went to wake the baby. His last feeding had been at midnight and she had not heard him stir since then. She found her son dead.

What happened? Why didn't we notice he was sick? What did we do wrong? John and Julie were in anguish. Their son had died of a condition known as Sudden Infant Death Syndrome (SIDS), a condition for which the medical profession cannot yet find a cause, even though the syndrome has been described since the late 1700s.

A concerted effort to find the cause of SIDS really began in early 1972, after persistent pressure from parents who had lost infants to this condition. Although we have learned a great deal about the circumstances leading up to SIDS, we still have not determined the cause and a way to prevent it.

Q: What is SIDS?

A: SIDS is the diagnosis given when an infant dies suddenly with no apparent cause. About 5,000 infants die of this disease every year in the United States. For every 1,000 American infants of each race born alive, 1.25 white and 2.82 African-American infants will die of SIDS.

In the past, pathologists who searched for clues during an autopsy could find only minor signs of congestion and inflammation in the airways; these seemed unlikely contributors.

The absence of a recognized cause or change in the infant has made it difficult to diagnose early signs of the disease.

The infants' lungs look like there has been an obstruction. This has led to theories that the large thymus glands in the chest or suffocation from external materials might be the cause. This latter hypothesis lead the English to call this disease "crib death." These factors do not explain most cases.

Recent findings have led pathologists to look for abnormalities that might have occurred during pregnancy. These include changes in the brain; birth defects and infections; a slow decline in fetal hemoglobin (which brings oxygen to the cells) after birth. We still do not have the answers. These observations have not led us to a method of determining which children are at risk.

A new study has linked a declining heart rate to some cases. Physicians from the Johns Hopkins University, the University of Maryland, and the Robert Wood Johnson School of Medicine in New Jersey discovered that heart rates in babies considered at high risk of SIDS dropped dramatically just before the babies stopped breathing.

Q: Who is at risk?

A: About 20 percent of SIDS babies are premature. SIDS most frequently strikes premature male infants between the ages of 1 and 4 months who are born into poor families to young mothers who have had multiple pregnancies. SIDS is twice as likely to occur in the fall and winter.

In a recent multicenter study by The National Institute of Child Health and Development (NICHD), researchers found a higher incidence of SIDS in infants born to mothers under the age of 20 who smoked cigarettes during pregnancy and/or used illicit drugs.

Low weight gain of the mother and infections of the urinary tract and vagina during pregnancy also increased the risk of SIDS. But these material factors do not explain all cases.

Q: What is being done?

A: In the United States, the effort to control this disease has focused on monitoring children who exhibit apnea: periods when the child turns blue or stops breathing. The evidence to date has not indicated that this method is effective.

The British have taken a different approach.

After classifying a child as high-risk, health professionals visit the child monthly for the first six months to determine his/her weight and health status and to intervene medically when necessary. The rate of SIDS-related deaths in Britain has dropped by half.

This monitoring method is obviously an expensive step for the health care system and still cannot prevent all deaths.

Around the world, teams of scientists continue to research the causes of SIDS so that we can eventually prevent all cases.

Q: How can we help patients who've lost their infants to SIDS?

A: These parents need support to cope with their loss. They need to know that other SIDS parents have asked the same questions they did and have learned how to dispel their feelings of guilt. The SIDS Alliance in Columbia can help; for information, call (800) 221-SIDS. In Baltimore, you can call the SIDS Counseling Project at 706-5062.

Dr. Genevieve Matanoski is a physician and epidemiologist at the Johns Hopkins School of Hygiene and Public Health. She is a founding director of the school's Institute for Women's Health Research and Policy.

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