Abstract 31

Objective: Temporal trends of US infant death due to malformations were examined to estimate its impact on infant mortality. Methods: U.S. birth data for 1986-91 revealed 23,812,981 live births and 229,569 infant deaths. Deaths caused by malformations (n=48,124) were categorized by 1) central nervous system (CNS), 2) cardiovascular (CV), 3) respiratory, 4) gastrointestinal (GI), 5) genitourinary (GU), 6) musculoskeletal (MSK), 7) chromosomal abnormalities, and 8) other. Malformation-specific infant mortality rates (M-S IMR) were expressed as deaths per million live births. Temporal trends for 3 consecutive time periods were studied: 1986-87 (period 1), 1988-89 (period 2), and 1990-91(period 3). Results: Overall M-S IMR significantly decreased by 3.7% (from 2,121 to 2,043 per million) between 1st and 2nd periods, and by 6.6% (from 2,043 to 1,908 per million) between the 2nd and 3rd periods. From period 1 to 2, only CNS malformations declined in M-S IMR. However, from 1st to 3rd periods, the M-S IMR declined for most malformations: CNS (15.6%), GU (14.6%), MSK (14.6%), CV(10.6%), respiratory (8.6%), and other (16.2%). Only chromosomal abnormalities showed a temporal increase in M-S IMR (6.9%). In the same time period, anencephaly showed a 25% reduction and renal agenesis a 15% reduction in M-S IMR. Reduction in deaths due to malformations contributed 18.2% of the overall net reduction in infant mortality between 1985-86 and 1990-91. Conclusion: M-S IMR has declined for most congenital malformations, most likely resulting from improved prenatal screening and perinatal/neonatal therapies.