TABLE 1

Characteristics of Infants in the Study Cohort Compared With All Other Infants

CharacteristicsStudy Cohort (n = 22 547)All Others (n = 259 351)P
Birth weight, mean (SD), g3332.0 (557.0)3473.0 (499.0)<.001a
Gestational age, mean (SD), wk38.4 (1.7)39.0 (1.3)<.001a
Maternal age, mean (SD), y29.4 (6.0)28.8 (6.0)<.001a
Length of stay, birth hospitalization, mean (SD), h70.7 (99.8)45.5 (59.8)<.001b
Length of stay, birth hospitalization if no phototherapy, mean (SD), h55.3 (73.1)44.9 (58.8)<.001b
Male, n (%)12875 (57)131123 (51)<.001c
Gestational age, n (%), wk<.001b
    351522 (7)2735 (1)
    362158 (10)6462 (2)
    372700 (12)14743 (6)
    383918 (17)36788 (14)
    395302 (24)71113 (27)
    404954 (22)84882 (33)
    ≥411993 (9)42628 (16)
Race, n (%)<.001c
    White9145 (41)118750 (46)
    Asian6008 (27)58854 (23)
    Hispanic4972 (22)43889 (17)
    Black1039 (5)22473 (9)
    Other1002 (4)11882 (5)
    Unknown381 (2)5697 (2)
AAP risk group, n (%)<.001c
    Low risk: ≥38 wk and not DAT positive14591 (65)232677 (90)
    Medium risk: <38 wk and not DAT positive6140 (27)23609 (9)
    Medium risk: ≥38 wk and DAT positive1576 (7)2734 (1)
    High risk: <38 wk and DAT positive240 (1)331 (0)
DAT, n (%)<.001c
    Negative12553 (56)50801 (20)
    Positive1816 (8)3065 (1)
    Not done8178 (36)205485 (79)
  • a P-value calculated by t test.

  • b P-value calculated by rank-sum test.

  • c P-value calculated by χ2 test.