Descriptive characteristics according to gestational age in Millennium Cohort Study children in England
| Gestational age group (weeks) | ||||||
|---|---|---|---|---|---|---|
| Total; N=7650 | <32; very preterm; N=84 | 32–33; moderately preterm; N=92 | 34–36; late preterm; N=471 | 37–38; early term; N=1596 | 39–41; full term; N=5407 | |
| Child characteristics | ||||||
| Male child (%) | 3881 (51) | 38 (46) | 55 (67) | 241 (52) | 831 (52) | 2716 (50) |
| White British (%) | 5944 (86) | 54 (71) | 73 (90) | 370 (87) | 1203 (84) | 4244 (87) |
| Mixed ethnicity (%) | 314 (4) | 7 (9) | 1 (1) | 26 (5) | 76 (4) | 204 (3) |
| Indian (%) | 266 (2) | 4 (4) | 7 (4) | 17 (2) | 47 (2) | 191 (2) |
| Pakistani or Bangladeshi (%) | 658 (4) | 11 (7) | 7 (2) | 31 (3) | 147 (5) | 462 (4) |
| Black or Black British (%) | 339 (3) | 7 (7) | 3 (2) | 24 (3) | 85 (4) | 220 (3) |
| Other ethnic group (%) | 128 (1) | 1 (2) | 1 (1) | 2 (0) | 38 (2) | 86 (1) |
| Multiple birth (%) | 195 (3) | 14 (17) | 23 (28) | 63 (14) | 77 (5) | 18 (0) |
| Caesarean delivery (%) | 1600 (21) | 48 (57) | 54 (64) | 174 (36) | 531 (33) | 793 (15) |
| Firstborn child (%) | 3194 (42) | 44 (55) | 49 (55) | 205 (44) | 582 (37) | 2314 (43) |
| Birth weight in kg, mean (SE) | 3.3 (0.6) | 1.2 (0.4) | 2 (0.4) | 2.6 (0.6) | 3.2 (0.5) | 3.5 (0.5) |
| Age when allowed home from hospital in weeks, mean (median) | 0.6 (0.3) | 8.6 (8.0) | 3.2 (3.0) | 1.4 (0.9) | 0.5 (0.4) | 0.4 (0.1) |
| Never breastfed (%) | 2119 (29) | 26 (28) | 25 (26) | 159 (35) | 488 (32) | 1421 (27) |
| Breastfed 0–1 months (%) | 2072 (27) | 23 (26) | 32 (30) | 155 (32) | 445 (28) | 1417 (26) |
| Breastfed 2–3 months (%) | 873 (11) | 16 (23) | 17 (22) | 47 (10) | 176 (11) | 617 (11) |
| Breastfed ≥4 months (%) | 2586 (33) | 19 (23) | 18 (22) | 110 (24) | 487 (29) | 1952 (36) |
| Oldest age group at school* (%) | 2600 (34) | 24 (25) | 30 (30) | 153 (33) | 563 (35) | 1830 (33) |
| Middle age group at school* (%) | 2447 (32) | 24 (32) | 23 (25) | 171 (34) | 532 (33) | 1697 (31) |
| Youngest age group at school* (%) | 2603 (34) | 36 (43) | 39 (44) | 147 (33) | 501 (31) | 1880 (35) |
| Maternal characteristics | ||||||
| Maternal age, mean (median) | 28.7 (6) | 28.2 (5.4) | 30.2 (5.8) | 29.0 (6.5) | 29.0 (6) | 28.7 (6) |
| Single mother (%) | 1065 (14) | 15 (18) | 9 (8) | 73 (15) | 218 (13) | 750 (14) |
| High education level† (%) | 2314 (32) | 25 (31) | 30 (35) | 132 (28) | 454 (29) | 1673 (33) |
| Medium education level† (%) | 1012 (14) | 9 (12) | 12 (14) | 59 (13) | 213 (13) | 719 (14) |
| Lower education level† (%) | 2974 (40) | 28 (34) | 39 (44) | 212 (47) | 618 (41) | 2077 (40) |
| Overseas/other qualification (%) | 242 (2) | 3 (2) | 1 (0) | 5 (1) | 53 (3) | 180 (3) |
| No formal qualifications (%) | 1103 (12) | 19 (20) | 8 (7) | 63 (12) | 258 (14) | 755 (11) |
| Highest social class‡ (%) | 2091 (29) | 18 (24) | 24 (30) | 135 (30) | 415 (28) | 1499 (30) |
| Intermediate social class‡ (%) | 1343 (18) | 16 (16) | 16 (16) | 79 (18) | 268 (17) | 964 (19) |
| Lowest social class‡ (%) | 285 (4) | 3 (4) | 3 (5) | 22 (5) | 58 (4) | 199 (4) |
| Never worked (%) | 387 (5) | 3 (3) | 9 (9) | 21 (5) | 89 (5) | 265 (5) |
| Only English spoken at home (%) | 6406 (91) | 68 (89) | 77 (94) | 408 (93) | 1331 (90) | 4522 (91) |
| Mostly English spoken at home (%) | 369 (3) | 8 (5) | 5 (2) | 30 (4) | 87 (4) | 239 (3) |
| English and other language spoken at home (%) | 875 (6) | 8 (6) | 10 (4) | 33 (3) | 178 (6) | 646 (6) |
| Smoked when pregnant (%) | 1496 (21) | 23 (24) | 15 (15) | 112 (24) | 330 (22) | 1016 (20) |
| Alcohol§ when pregnant (%) | 510 (7) | 2 (2) | 8 (9) | 36 (9) | 98 (6) | 366 (7) |
↵* Oldest age group at school is defined as born in months 1–4 (Sep–Dec), middle age group is born in months 5–8 (Jan–Apr) and youngest age group is born in months 9–12 (May–Aug).
↵† High education level is defined as bachelor's degree or equivalent, medium education is ‘A level’ or equivalent qualifications usually at the end of secondary school at age 18 and lower education level is qualifications equivalent to those at the end of compulsory schooling at age 16.
‡ Highest social class is managerial/professional occupations, lowest social class is routine and semiroutine occupations and intermediate is the remaining occupations.
↵§ Moderate or high alcohol in pregnancy as defined in Kelly et al.39