Risk of childhood cancer for infants with birth defects. II. A record-linkage study, Iowa, 1983-1989

To attempt to confirm associations found in a companion study in Atlanta, Georgia between Down's syndrome and acute leukemia and between pyloric stenosis and childhood cancer, the authors used the State Health Registry of Iowa to link the records of infants and children with cancer for 1983 to 1989 with the records of infants with birth defects for 1983 to 1988. During the study period, birth defects were diagnosed in 10,891 infants younger than 1 year of age, and cancer was diagnosed in 396 children younger than 8 years of age. The authors compared the observed number of children with a defect who developed cancer with the number expected on the basis of the cancer registry rates. Of the 10,891 children with birth defects, 16 developed cancer (standardized incidence ratio (SIR) = 2.0, 95% confidence interval (CI) 1.2-3.3). Of 251 children with Down's syndrome (trisomy 21), two developed leukemia (SIR = 32.1, 95% CI 3.9-116.0). None of the infants with cancer had pyloric stenosis (SIR = 0.0, 95% CI 0.0-6.7). The results of this study supported the association found in the Atlanta study between Down's syndrome and leukemia, but did not support the association found there between pyloric stenosis and childhood cancer. This study, however, had a shorter follow-up period and a smaller number of subjects than the Atlanta study.