Mortality associated with birth defects: influence of successive disease classification revisions.

INTRODUCTION: The National Vital Statistics System is the fundamental source of mortality statistics in the United States. The cause-of-death classification which is used to assign medical terms to a standard taxonomy is revised periodically, and it is necessary to account for these changes when investigating trends. This paper presents birth defects mortality statistics and preliminary information on the most recent transition between revisions of the classification.
METHODS: Descriptive statistics are presented using multiple cause and underlying cause counts, rankings of leading causes of death, infant mortality rates, and age-adjusted death rates. Comparability results are based upon records that have been coded using two separate classifications.
RESULTS: Birth defects remain the leading cause of death for infants and among the leading causes for younger age groups. The trend for birth defect mortality shows that the risk of dying from birth defects decreased between 1950 and 2000. The effect of implementing successive revisions of the cause-of-death classification was relatively minor until the implementation of the most recent revision. Fewer records are assigned to birth defects in the latest revision than in the previous revision. DISCUSSION: Researchers investigating mortality trends related to birth defects need to be aware that the cause-of-death classification changes periodically. The effect of the changes between two successive classifications can be measured and explained.