TABLE 4

Characteristics of the 4 Clusters for Longitudinal Changes in WISC-III Vocabulary Raw Scores

Cluster ACluster BCluster CCluster D
n516511677
Proportion of total preterm cohort, %, n = 30917213825
Child characteristics
    Gestational age, mean (SD), wk27.9 (1.9)28.0 (1.9)28.0 (1.9)27.9 (2.0)
    Birth weight, mean (SD), g950 (173)969 (172)968 (157)905 (192)
    Male gender, n (%)27 (53)38 (58)62 (53)41 (53)
    Multiple, n (%)9 (18)12 (18)31 (27)16 (21)
    Small for gestational age, n (%)11 (22)17 (26)29 (25)17 (22)
    Maternal steroids, n (%)21 (41)23 (35)43 (37)23 (30)
    Indomethacin, n (%)25 (49)31 (48)59 (52)39 (53)
    Bronchopulmonary dysplasia, n (%)19 (38)32 (49)50 (43)39 (51)
    Neonatal brain injury, n (%)
        None41 (80)48 (74)93 (80)49 (64)
        Severe brain injurya6 (12)4 (6)3 (3)14 (18)
    NSI, n (%)b6 (12)8 (12)7 (6)22 (29)
Family factors
    Maternal age at birth, mean (SD), y30.0 (6.0)27.2 (5.6)27.9 (5.9)27.0 (6.0)
    Maternal education, n (%)
        High school or less7 (14)28 (43)39 (34)48 (62)
        ≥1 year of college44 (86)37 (57)76 (66)29 (38)
    Race and ethnicity, n (%)
        Non-Hispanic white44 (86)44 (68)78 (67)45 (59)
        Others7 (14)21 (32)38 (33)31 (41)
    Bilingual environment, n (%)6 (12)8 (12)12 (10)15 (20)
    Single-parent household at the age of 16 y, n (%)12 (24)22 (34)32 (28)35 (45)
  • a Severe brain injury includes grades 3 to 4 intraventricular hemorrhage, periventricular leukomalacia, and grade 2 and above ventriculomegaly.

  • b NSI includes the presence of any of the following: abnormal neurological examination including cerebral palsy, ventriculo peritoneal shunt, seizure disorder, hearing aids, services for the blind.