As part of its epidemiologic studies of congenital malformations, the Centers for Disease Control (CDC) conducts two birth defects surveillance systems in the United States. The Metropolitan Atlanta Congenital Defects Programme (MACDP) is an intensive surveillance system using several methods to identify infants born with birth defects in the Atlanta area. The Birth Defects Monitoring Programme (BDMP) is a nationwide surveillance system that monitors 1 million births per year, about a third of all births in the U.S. It relies on diagnoses from newborn discharge summaries to ascertain affected infants. The systems were originally designed to detect potential 'epidemics' of birth defects that could occur following the widespread dissemination of new teratogens similar to thalidomide. In addition to monitoring, they have also proved to be useful resources for a variety of studies of the epidemiology of birth defects.

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.

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