TABLE 1

Characteristics of the Study Cohort According to Length of Gestation

Late Preterm (34 wk 0 d to 36 wk 6 d), n = 486 (5.4%)Term (37 wk 0 d to 41 wk 6 d), n = 8507 (94.6%)P Value (t test or χ2)
Mean/nSD/%Mean/nSD/%
Gender, women22446.1%400147.0%.69
Birth weight, ga29394753426442<.001
Relative birth weight, SDa,b−0.121.10.051.0<.001
Gestational wk<.001
 34 wk 0 d to 34 wk to 6 d881.000
 35 wk 0 d to 35 wk to 6 d1471.600
 36 wk 0 d to 36 wk to 6 d2512.800
 37 wk 0 d to 37 wk to 6 d0012566.6
 38 wk 0 d to 38 wk to 6 d00242714.0
 39 wk 0 d to 39 wk to 6 d00262227.0
 40 wk 0 d to 40 wk to 6 d00160829.2
 41 wk 0 d to 41 wk to 6 d0059417.9
Year of birth<.001
 1934–1935438.8%5106.0%
 1936–19376713.8%88510.4%
 1938–19396613.6%124614.6%
 1940–194114830.5%191922.6%
 1942–194310822.2%268531.6%
 19445411.1%126214.8%
Birth order, first born27556.6%414848.8%<.001
Mother’s age, ya27.85.828.45.4.014
Mother’s BMI at the deliverya25.52.826.22.8<.001
Father’s occupational statusc.008
 Manual worker31963.8%520861.2%
 Junior clerical11924.5%215525.3%
 Senior clerical5711.7%114413.4%
SEP in adulthood
 Occupationd<.001
  Manual worker9821.5%118314.8%
  Junior clerical17037.4%314239.3%
  Senior clerical18741.1%366945.9%
 Education.03
  Basic or upper secondary35372.6%567866.7%
  Lower tertiary8918.3%192722.7%
  Higher tertiary449.1%90210.6%
 Income tertilese.002
  Lowest19139.5%272232.1%
  Intermediate15732.5%290534.3%
  Highest13528.0%284233.6%
Social mobility from father’s occupational category in childhood to adult SEP category
 Occupation.23
  Downward357.7%4996.2%
  Stable15033.0%246730.9%
  Upward27059.3%502862.9%
 Education.29
  Downward11423.5%204924.1%
  Stable30061.7%498858.6%
  Upward7214.8%147017.3%
 Income.03
  Downward7014.4%116813.7%
  Stable21043.2%321237.8%
  Upward20642.4%412648.5%
  • a Mean (SD).

  • b Relative birth weight refers to birth weight adjusted length of gestation by linear regression, expressed in SD units.

  • c Highest occupational status as obtained from birth, child welfare clinic, and school health care records.

  • d Missing n = 544.

  • e Missing n = 41.