MEDICAL BIOLOGY: ON SUDDEN INFANT DEATH SYNDROME

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MEDICAL BIOLOGY: ON SUDDEN INFANT DEATH SYNDROME

Notes by ScienceWeek:

The "fetoproteins" are fetal proteins found in small amounts in adults. Alpha-fetoprotein is normally produced during the 12th to 15th week of gestation, decreasing thereafter, but appearing in the blood when certain tumors are present.

The following points are made by G.C. Smith et al (New Engl. J. Med. 2004 351:978):

1) The sudden infant death syndrome (SIDS) is defined as the death of an infant during the first year of life in cases in which all identifiable causes of death can be ruled out by appropriate assessment. Observational studies have highlighted the prone sleeping position and environmental tobacco smoke in the infant's bedroom as factors that are associated with SIDS.(1) Widespread public health campaigns directed at modifying these behaviors have been followed by a sharp reduction in the incidence of SIDS. However, SIDS remains the most important single cause of infant death in the industrialized world.(1,2)

2) A number of studies have identified obstetrical factors that are associated with an increased risk of SIDS, such as poor intrauterine growth and premature birth.(1) Moreover, as programs designed to address environmental risk factors have become widespread, the relative importance of obstetrical determinants has increased.(3) The mechanisms linking complications of pregnancy and the risk of SIDS remain obscure.

3) Previous studies have suggested similarities between unexplained stillbirth and SIDS with respect to clinical and pathological findings, suggesting that the two conditions may be related.(4,5) A raised maternal serum level of alpha-fetoprotein during the second trimester of pregnancy is one of the best biochemical predictors of the risk of unexplained stillbirth. If SIDS and unexplained stillbirth have common pathophysiological determinants, there might be a direct association between maternal serum alpha-fetoprotein levels and the risk of SIDS.

4) The authors designed a study to test the hypothesis that the risk of SIDS would increase with increasing maternal serum levels of alpha-fetoprotein in a large Scottish database linking biochemical, pregnancy, birth, and death records for 214,532 live-born singleton infants.

5) The authors conclude: "There is a direct association between second-trimester maternal serum alpha-fetoprotein levels and the risk of SIDS, which may be mediated in part through impaired fetal growth and preterm birth."

References (abridged):

1. Sullivan FM, Barlow SM. Review of risk factors for sudden infant death syndrome. Paediatr Perinat Epidemiol 2001;15:144-200. [Erratum, Paediatr Perinat Epidemiol 2002;16:96.]

2. Scottish perinatal and infant mortality report 2000. Edinburgh: Information and Statistics Division NHS Scotland, 2001

3. Alm B, Norvenius SG, Wennergren G, et al. Changes in the epidemiology of sudden infant death syndrome in Sweden 1973-1996. Arch Dis Child 2001;84:24-30

4. Walsh S, Mortimer G. Unexplained stillbirths and sudden infant death syndrome. Med Hypotheses 1995;45:73-75

5. Fifer WP, Myers MM. Sudden fetal and infant deaths: shared characteristics and distinctive features. Semin Perinatol 2002;26:89-96

New Engl. J. Med. http://www.nejm.org

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