Table 1.

Differences in Patient Populations

Lubchenco et al1Usher et al2Brenner et al6Pediatrix Medical Group
Dates of measurement1948–19611959–19631962–19691996–1998
n 563530030 77227 028
Male neonatesN/A145N/A11 918
Female neonatesN/A155N/A15 110
RaceWhiteWhiteWhite/non-white, 98% of
non-white were black
Socioeconomic levelMedically indigent
or partial pay
AltitudeDenverSea level<600 ftContinental United States—
sea level → 5280 ft
ExclusionsMajor congenital
Major congenital anomalies,
erythroblastosis, infant of
a diabetic mother, and
marked fetal malnutrition
IntervalsWeeklyGrouped at EGA: 24–26 wk,
27–28 wk, 29–30 wk,
31–32 wk
Weekly from 2 through
44 wk
Weekly from 22 through
42 wk
  • N/A indicates not available.