TABLE 1

Observed Mortality Rates by Year and Birth Weight Category for Infants 501 to 1500 g From 2000 to 2009 (N = 355 806)a

Weight, g2000, %2001, %2002, %2003, %2004, %2005, %2006, %2007, %2008, %2009, %P Valuea
n = 27 125n = 27 498n = 29 352n = 31 476n = 34 772n = 37 227n = 39 854n = 41 653n = 43 283n = 43 566
All 501–1500 14.114.315.014.414.214.013.913.712.912.5<.001
501–750 41.743.144.042.243.241.241.539.839.236.6<.001
751–1000 13.013.313.914.513.513.513.413.812.611.7<.001
1001–1250 6.35.95.85.95.46.05.45.95.35.7<.001
1251–1500 3.53.43.83.63.33.53.93.43.33.5.112
  • Mortality data were missing for 0.3% of infants.

  • a P values correspond to the test for linear trend across years, after adjusting for infant characteristics by using logistic regression.