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Empirical (A) and calculated (B) weight-specific mortality curves are shown for births at 33, 35, and 37 weeks of gestation; weeks 33 and 35 are based on clinical estimates of gestation, while week 37 is based on the date of the last menstrual period. Simulation parameters are shown in Table 2. Empirical data are based on National Center for Health Statistics data, US livebirths, 1995–2002.
