Table 1

Characteristics of Millennium Cohort Study children included in age 11 analysis*

TotalGestational age at birthP values†
<32 weeks32–33 weeks34–36 weeks37–38 weeks39–41 weeks
Very pretermModerate pretermLate pretermEarly termFull term
Age 11 analysis11 690n=106 (1.0%)n=106 (0.9%)n=618 (5.8%)n=2327 (20.1%)n=8533 (72.3%)
Gestational age in weeks, mean (SD)39.1 (1.9)28.6 (1.9)32.7 (0.5)35.3 (0.7)37.7 (0.5)40.0 (0.8)<0.01
Age at interview, mean (SD)11.2 (0.3)11.1 (0.3)11.1 (0.4)11.2 (0.3)11.2 (0.3)11.2 (0.3)0.8
Female, n (%)5807 (48.8)54 (46.0)45 (33.9)288 (46.8)1118 (47.5)4302 (49.6)0.03
Ethnicity, n (%)
 White9806 (85.3)81 (79.1)85 (87.3)511 (85.2)1903 (83.1)7226 (86.0)0.03
 Black and Minority Ethnic groups1884 (14.7)25 (20.9)21 (12.7)107 (14.8)424 (16.9)1307 (14.0)
Birth weight in grams, mean (SD)‡3347.1 (572.7)1226.7 (399.6)2057.3 (497.9)2660.2 (490.4)3166.4 (482.7)3496.2 (463.9)<0.01
Household’s national statistics socioeconomic classification, n (%)
 Managerial and professional3471 (26.7)34 (30.4)25 (23.2)171 (25.3)648 (24.6)2593 (27.4)
 Intermediate2480 (21.1)19 (15.0)20 (19.5)139 (21.0)480 (20.1)1822 (21.5)0.3
 Routine and manual4579 (42.5)45 (46.3)50 (51.1)240 (43.4)960 (45.1)3824 (41.6)
 Never worked/long-term unemployed1160 (9.7)8 (8.4)11 (6.1)68 (10.2)239 (10.3)834 (9.5)
Household’s area deprivation score, n (%)
 Top quintile1897 (16.9)19 (25.7)13 (21.9)103 (30.0)355 (26.5)1407 (26.1)
 Fourth quintile1688 (16.8)20 (24.1)22 (22.4)76 (18.2)343 (19.7)1227 (20.2)
 Third quintile2058 (20.0)13 (10.8)16 (18.9)108 (20.3)415 (20.9)1506 (19.8)0.44
 Second quintile2595 (20.0)21 (21.0)23 (23.6)121 (13.5)517 (17.4)1913 (16.7)
 Bottom quintile3452 (26.4)33 (18.5)32 (13.2)210 (18.0)697 (15.5)2480 (17.1)
Maternal education, n (%)§
 Higher (university degree or equivalent)3811 (28.5)30 (28.8)29 (24.2)182 (24.9)709 (25.8)2861 (29.6)
 Medium (A-level or equivalent)1711 (13.8)10 (7.7)11 (10.6)76 (12.5)348 (14.0)1266 (14.0)
 Lower (GCSE or equivalent/overseas)4608 (42.6)43 (38.6)52 (53.1)269 (44.2)926 (43.5)3318 (42.1)<0.01
 No formal qualification1554 (15.1)23 (24.9)14 (12.3)91 (18.5)344 (16.7)1082 (14.2)
Maternal age at delivery (years) mean (SD)28.1 (6.0)27.8 (6.0)28.6 (6.3)27.8 (6.0)28.3 (6.0)28.1 (6.0)0.94
Mother lone parent, n (%)1692 (16.8)17 (16.3)15 (13.3)113 (21.7)342 (16.6)1205 (16.6)0.11
Smoking during pregnancy, n (%)
 Never smoked7827 (63.2)67 (63.6)59 (53.9)379 (56.7)1566 (63.0)5756 (63.9)
 Gave up1404 (12.8)13 (9.8)14 (11.9)74 (12.4)257 (12.3)1046 (13.0)0.02
 Kept smoking2459 (24.1)26 (26.6)33 (34.2)165 (31.0)504 (24.8)1731 (23.1)
Alcohol use during pregnancy, n (%)
 Never8187 (69.1)82 (75.9)84 (76.3)451 (70.3)1696 (72.0)5874 (68.1)
 Light (1–2 units per week or per occasion)2702 (23.7)19 (18.9)14 (15.8)126 (21.6)489 (21.6)2054 (24.6)0.1
 Moderate to heavy (3 or more units per week or per occasion)801 (7.2)5 (5.2)8 (7.9)41 (8.1)142 (6.5)605 (7.4)
Duration of breast feeding, n (%)
 Never breast fed 3596 (34.8)33 (33.4)33 (35.1)222 (42.9)765 (37.0)2543 (33.5)
 <1 month2287 (17.8)15 (16.2)21 (18.0)126 (17.3)473 (17.9)1652 (17.7)
 1–3 months2036 (16.9)33 (29.6)27 (24.0)122 (18.0)411 (17.9)1443 (16.3)<0.01
 4+ months3771 (30.6)25 (20.9)25 (22.9)148 (21.9)678 (27.2)2895 (32.5)
Birth order, n (%)
 First born4896 (41.9)52 (50.4)48 (46.7)272 (41.4)855 (38.1)3669 (42.8)0.01
Type of delivery, n (%)¶
 Normal8050 (70.6)40 (41.8)46 (41.5)351 (58.0)1422 (62.5)6191 (74.6)
 Assisted1139 (9.4)5 (3.8)5 (4.6)47 (8.8)142 (5.8)940 (10.6)<0.01
 Caesarean2480 (20.0)60 (54.4)55 (55.0)220 (33.3)760 (31.7)1385 (14.8)
 Family history of asthma, n (%)2921 (26.3)22 (24.6)34 (34.2)162 (25.2)560 (25.0)2143 (26.6)0.41
  • Unweighted counts and survey-weighted proportions reported.

  • *Similar demographics at age 7 analysis, not included.

  • †From weighted test for association.

  • ‡Ten birth weight data missing.

  • §Six maternal qualification data missing.

  • ¶Twenty one type of delivery data missing.

  • GCSE, General Certificate of Secondary Education.