  Objective: To exploit state variations in infant mortality, identify
diagnoses that contributed to reduction of the infant mortality rate (IMR), and
examine factors associated with preterm related mortality rate (PMR). Methods:
Using linked birth-infant deaths files, we examined patterns in the leading
causes of IMR. We compared these rates at both national and state levels to
find reduction trends. Creating a cross-sectional time series of states' PMR
and some explanatory variables, we implemented a fixed-effect regression model.
Results: We found substantial state-level variations in changes of the IMR
(range= -2.87 to 2.08) and PMR (-1.77 to 0.67). Twenty-one states in which the
IMR declined more than the national average of 0.99 (6.89 to 5.90) were labeled
as successful. In the successful states, we found a reduction in the PMR
accounted for the largest decline in the IMR (0.90 fewer deaths). Changes in
the other subgroups of leading causes did not differ significantly in
successful and unsuccessful states. Policy Implications: Although its impact is
not large, reducing the percentage of pregnant women with inadequate care is
one of the mechanisms through which the PMR might decrease.
