FETAL GROWTH-RETARDATION IN SUDDEN-INFANT-DEATH-SYNDROME (SIDS) BABIES AND THEIR SIBLINGS

To evaluate the intrauterine growth potential of infants that die from sudden infant death syndrome (SIDS), the authors compared SIDS infant s with their surviving siblings. The SIDS sibships themselves were als o compared with sibships where all infants survived. Data from the pop ulation-based Medical Birth Registry of Norway, with 1.3 million birth s during 1967-1988, were used. From the birth cohorts, 1,984 SIDS case s were identified. All births were linked into sibships. The mean birt h weight and gestational age were calculated across sibships of differ ent sizes for first to fourth birth order. In a further analysis, birt h weights were standardized to adjust for gestational age. Mothers of SIDS infants gave birth to smaller babies in general. SIDS infants wei ghed, on average, 85 g less at birth than their siblings and 164 g les s compared with babies in nonaffected sibships. When birth weights wer e standardized for gestational age, most of the weight difference betw een SIDS infants and siblings was due to a shorter gestational age of SIDS infants, while the difference between surviving siblings of SIDS infants and births from nonaffected sibships remained. All births in s ibships with a SIDS infant were intrauterine growth retarded. This may reflect factors that contribute to SIDS risk (such as maternal smokin g). The factors that contribute to shorter gestational age and further slowing of growth in the SIDS infants may specificalIy influence the SIDS infant and not its siblings.