Weight gain and sudden infant death syndrome: changes in weight z scores may identify infants at increased risk

Aims-To investigate patterns of infant growth that may influence the risk o f sudden infant death syndrome (SIDS). Design-Three year population based case control study with parental intervi ews for each death and four age matched controls. Growth was measured from prospective weight observations using the British 1990 Growth Reference. Setting-Five regions in England (population greater than 17 million, more t han 470 000 live births over three years). Subjects-247 SIDS cases and 1110 controls. Results-The growth rate from birth to the final weight observation was sign ificantly poorer among the SIDS infants despite controlling for potential c onfounders (SIDS mean change in weight z score (delta zw) = -0.38 (SD 1.40) v controls = +0.22 (SD 1.10), multivariate: p < 0.001). Weight gain was po orer among SIDS infants with a normal birth weight (above the 16th centile: odds ratio (OR) = 1.75, 95% confidence interval (CI) 1.48-2.07, p < 0.0001 ) than for those with lower birth weight (OR = 1.09, 95% CI 0.61-1.95, p = 0.76). There was no evidence of increased growth retardation before death. Conclusions-Poor postnatal weight gain was independently associated with an increased risk of SIDS and could be identified at the routine six week ass essment.