Blood imbalance detected in SIDS victims.

Blood imbalance detected in SIDS victims

Sudden infant death syndrome(SIDS), in which the tragedy of a baby dying is compounded by the lack of any clear-cut medical reason, is one of the most frustrating mysteries for medical researchers. The infant, usually between 2 and 4 months of age, simply stops breathing. Researchers have observed in retrospect that "at risk" babies tended to be of low birthweight, required longer hospitalization at birth and had lower Apgar scores -- which reflect reflexes, muscle tone and respiratory function--and that their mothers may have had anemia or taken drugs during pregnancy. But such factors are only very loosely correlated with the syndrome and by no means predict that a particular baby will succumb to SIDS.

Now, another clue has been added--onethat researchers say might eventually help in screening for potential SIDS victims. University of Wisconsin at Madison scientists report they have found elevated levels of hemoglobin F (fetal) in the blood of infants whose cause of death was listed as SIDS. They found that the mean proportion of hemoglobin F to hemoglobin A (adult) in 59 SIDS victims was 63 percent, compared with a mean of 48 percent in 40 age-matched control infants. "Normally, hemoglobin F is largely replaced by adult hemoglobin . . . during the first six months after birth," researchers Enid F. Gilbert, Richard L. Moss and Gary G. Giulian write in the April 30 NEW ENGLAND JOURNAL OF MEDICINE.

They suggest that "infants with SIDSare characterized by a marked delay in the switch from hemoglobin F to hemoglobin A -- a phenomenon that may reflect an underlying chronic condition." The imbalance, they add, could affect "the delivery of oxygen to sensitive tissue sites."

The Wisconsin researchers concludethat hemoglobin F levels may be valuable not only as a "postmortem indicator" of SIDS but also "as a prospective marker for some infants at risk for SIDS."

The findings are "a valuable firststep," says Marie Valdes-Dapena, president of the National SIDS Foundation in Landover, Md., and a pathologist at the University of Miami School of Medicine. But she stresses that the findings must be replicated.

Beyond that, Valdes-Dapena echoesthe dilemma of those looking for ways to prevent SIDS. "It would be helpful to have a blood test," she says. But if the test showed an infant was at high risk, she asks, "Then what?"