Vulnerable infants
by Ralph A. Franciosi, MD
Ralph Franciosi, MD, was medical adviser for the Infant Death Center of Wisconsin and pathologist at Children's Hospital of Wisconsin. He also was a professor of Pathology and Laboratory Medicine at the Medical College of Wisconsin.
When an infant dies, we expect signs of a serious illness. Since this is not the case in Sudden Infant Death Syndrome (SIDS), the death used to be presumed to occur in a "normal, healthy" infant, giving the aura of mystery. This is no longer the case.
Careful, time-consuming and costly research has revealed structural abnormalities in the portion of the brain (the brainstem) that is responsible for the control of breathing, heart rate, arousal from sleep and other vital functions. We now know that, although the SIDS event occurs after birth, the cause originates in fetal development.
The brainstem, as mentioned, is the portion of the brain essential to maintaining vital functions. These functions are controlled by a circuit of nerves that relay information to the brain. Vital functions are involuntary in a normal infant and depend on the full development of this neural system.
Research has uncovered structural abnormalities in the nerve process of SIDS infants, indicating the infant's interneuronal communication has not developed past the fetal state. The result is delays in the transmission of messages to the brain regarding vital functions.
An additional abnormality in the brainstem involves the nerve cells themselves. The nerve cells in a SIDS infant have a defect in the receptors which perceive the rise in carbon dioxide in the bloodstream. If carbon dioxide levels become elevated, a normal infant will sense the elevation, send the message to the brain and arouse from sleep. However, an infant with a defect in these receptors does not.
It is believed SIDS victims are made vulnerable to a SIDS episode by prenatal conditions which delay or damage the infants neural communication system. These prenatal conditions (see table below) are labeled risk factors because they increase the incidence of SIDS.
Our approach to prevent SIDS is to identify and decrease prenatal risk factors. These factors create a greater risk when they occur in combination. However, it is important to mention, not all infants exposed to the known risk factors are made vulnerable or will die of SIDS.
|
Risk Factors |
Number of Cases per 1000 Live Births |
| Less than 37 weeks gestational age (premature births) |
3.1 |
| Less than 2,500 grams birth weight |
4.5 |
| Maternal age less than 20 years |
3.0 |
| Education less than high school |
3.4 |
| Not married |
3.0 |
| Prenatal care started in the second or third trimester or no prenatal care |
2.6 - 3.9 |
| Maternal smoking |
3.5 |
| African American |
4.2 |
| American Indian |
1.9 |
| Overall |
1.4 |
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