Evidence for retarded kidney growth in sudden infant death syndrome.

The aim of the study was to compare the growth rate of the kidneys of infants who died of sudden infant death syndrome (SIDS) and control babies under 1 year; 227 infants who died in St. Petersburg from 1983 to 1990 and who met the criteria for SIDS were included in the study; 138 infants who died suddenly of respiratory infections within the same period constituted a control group. The infants did not have signs of dehydration, malformations, tumours or intrauterine infections. Morphologically the kidneys were intact. Factors which might influence the weight of the kidneys at the time of death were: the cause of death (whether SIDS or not), gender, gestational age, weight, length and ponderal index at birth, age, weight and length at death. Stepwise (forward) linear regression analysis identified three variables which in combination most accurately and independently influenced the predicted weight of the kidneys. These were the cause of death, gender and weight at the time of death. The weight of the kidneys increased by 6.0 g for each increase in total body weight of 1,000 g [95% confidence interval (CI) 5.0-7.0 g], in boys the kidney weight was 3.3 g (95% CI 1.6-5.0 g) higher than in girls and in the SIDS babies kidney weight was 2.5 g (95% CI 0.8-4.2 g) less than controls. Delayed kidney growth may be an indicator of increased risk of SIDS in infants under 1 year and may contribute in some cases.