TABLE 2.

Calculation of Numbers of Impaired and Unimpaired Additional Survivors in Period II (500–999-g Birth Weight)

Period IPeriod II
Live births, no.496682
Deaths, no. (%)254 (51)222 (33)
Survived to 20 mo, no. (%)242 (49)460 (67)
Lost to follow-up monitoring, no.2843
Monitored to 20 mo, no.214417
    Unimpaired158267
    Impaired*56150
  • For period I (1982–1989), impairment rate = 56/214 (26%). Of 100 born, 49 survived. No. impaired = 26/100 × 49 = 13. No. unimpaired = 49 − 13 = 36. For period II (1990–1998), impairment rate = 150/417 (36%). Of 100 born, 67 survived. No. impaired = 36/100 × 67 = 24. No. unimpaired = 67 − 24 = 43. Comparing period II with period I, survival improvement = 67 − 49 = 18 additional survivors per 100 live births; impaired = 24 − 13 = 11 impaired survivors per 100 live births; unimpaired = 43 − 36 = 7 unimpaired survivors per 100 live births.

  • * MDI of <70 and/or neurosensory impairment.