Characteristics of the study participants according to their breastfeeding duration (n=4940)* among children from the UK Millennium Cohort Study (England)
| Characteristics | Descriptive | Duration of any breastfeeding | P value† | |||||
| Whole sample | Never BF (n=1200) (32.8%) | <2 months (n=1253) (33.9%) | 2 to <4 months (n=564) (10.6%) | 4 to <6 months (n=543) (9.3%) | 6 to<12 months (n=811) (13.9%) | ≥12 months (n=569) (9.5%) | ||
| n (%) | n (%) | n (%) | n (%) | n (%) | n (%) | n (%) | ||
| Pregnancy and child-related | ||||||||
| Gestational age at birth‡ | 39.8 (1.3) | 39.8 (1.1) | 39.8 (1.4) | 39.8 (1.3) | 39.9 (1.3) | 39.9 (1.4) | 39.8 (1.3) | 0.067 |
| Female | 2517 (49.9) | 641 (52.3) | 606 (46.9) | 291 (50.9) | 273 (48.0) | 401 (47.3) | 305 (54.1) | 0.015 |
| Age at key stage 4‡ | 16.2 (0.3) | 16.2 (0.3) | 16.2 (0.3) | 16.2 (0.3) | 16.2 (0.3) | 16.2 (0.3) | 16.2 (0.3) | 0.296 |
| No older siblings | 2492 (51.2) | 546 (48.0) | 717 (58.4) | 326 (56.6) | 291 (53.0) | 378 (47.2) | 234 (42.6) | <0.001 |
| Smoked during pregnancy | ||||||||
| Never | 3515 (64.4) | 703 (51.8) | 815 (58.9) | 390 (64.8) | 426 (74.9) | 679 (81.6) | 502 (85.6) | <0.001 |
| Gave up | 601 (13.4) | 148 (12.8) | 182 (16.1) | 87 (17.6) | 68 (13.0) | 70 (9.6) | 46 (9.9) | |
| Kept smoking | 824 (22.2) | 349 (35.4) | 256 (25.0) | 87 (17.6) | 49 (12.1) | 62 (8.8) | 21 (4.6) | |
| Moderate/heavy alcohol in pregnancy§ | 370 (7.7) | 94 (8.0) | 89 (7.4) | 31 (6.2) | 41 (7.2) | 70 (8.4) | 45 (8.3) | 0.745 |
| Sociodemographic, age 9 m. | ||||||||
| Maternal age (years)‡ | 29.8 (6.0) | 27.7 (5.2) | 29.2 (5.9) | 30.2 (6.0) | 31.9 (5.5) | 32.2 (5.6) | 32.7 (5.7) | <0.001 |
| Maternal education¶ | ||||||||
| Higher (NVQ 4 and 5) | 1551 (25.0) | 131 (7.7) | 316 (22.3) | 173 (26.7) | 260 (42.5) | 392 (44.5) | 279 (44.3) | <0.001 |
| Medium (NVQ 3) | 471 (8.5) | 59 (4.0) | 123 (8.7) | 71 (12.1) | 55 (10.3) | 93 (11.3) | 70 (13.5) | |
| Lower (NVQ 1 and 2) | 2238 (49.2) | 729 (59.9) | 653 (53.6) | 262 (51.0) | 180 (37.2) | 256 (35.8) | 158 (30.3) | |
| Other/overseas | 112 (2.0) | 25 (1.4) | 16 (1.4) | 16 (3.2) | 14 (2.9) | 22 (2.2) | 19 (3.9) | |
| None | 568 (15.3) | 256 (27.0) | 145 (14.0) | 42 (7.0) | 34 (7.1) | 48 (6.2) | 43 (8.0) | |
| Highest parental social class | ||||||||
| Managerial/professional | 2477 (44.2) | 332 (23.2) | 563 (42.6) | 300 (51.7) | 357 (62.9) | 552 (66.1) | 373 (62.1) | <0.001 |
| Intermediate | 1348 (28.2) | 399 (30.6) | 389 (32.7) | 160 (28.0) | 124 (25.0) | 157 (21.2) | 119 (22.7) | |
| Semiroutine/routine | 921 (22.6) | 386 (37.5) | 256 (20.9) | 87 (17.1) | 51 (10.7) | 81 (10.2) | 60 (11.7) | |
| Not applicable | 194 (5.0) | 83 (8.7) | 45 (3.8) | 17 (3.2) | 11 (1.4) | 21 (2.6) | 17 (3.6) | |
| Mother working | 2571 (49.4) | 506 (38.7) | 665 (52.0) | 329 (59.3) | 343 (63.1) | 458 (56.1) | 270 (45.5) | <0.001 |
| Maternal relationship status | ||||||||
| Married | 3220 (57.9) | 601 (41.4) | 787 (58.2) | 377 (63.7) | 389 (68.3) | 625 (74.5) | 441 (73.4) | <0.001 |
| Cohabitation | 1196 (27.9) | 372 (34.6) | 328 (29.3) | 133 (25.9) | 113 (23.0) | 154 (20.8) | 96 (18.1) | |
| Single mother | 524 (14.2) | 227 (24.0) | 138 (12.5) | 54 (10.4) | 41 (8.7) | 32 (4.7) | 32 (8.5) | |
| Maternal ethnicity: White | 4174 (89.6) | 1082 (93.9) | 1069 (90.9) | 459 (85.8) | 439 (85.6) | 677 (87.7) | 448 (82.5) | <0.001 |
| Language spoken at home | ||||||||
| English only | 4305 (92.0) | 1100 (95.1) | 1105 (93.2) | 483 (90.3) | 452 (88.4) | 705 (91.4) | 460 (84.8) | <0.001 |
| English+other language | 635 (8.0) | 100 (4.9) | 148 (6.8) | 81 (9.7) | 91 (11.6) | 106 (8.6) | 109 (15.2) | |
| Index of Multiple Deprivation | ||||||||
| Poorest quintile | 1248 (22.8) | 437 (34.8) | 335 (21.3) | 119 (16.3) | 94 (13.5) | 156 (14.7) | 107 (13.2) | <0.001 |
| Second quintile | 1089 (20.3) | 309 (24.8) | 269 (19.0) | 132 (21.5) | 120 (18.9) | 139 (14.1) | 120 (17.0) | |
| Middle quintile | 989 (21.7) | 224 (19.9) | 264 (23.4) | 104 (21.4) | 125 (25.0) | 168 (22.0) | 104 (20.7) | |
| Fourth quintile | 823 (18.4) | 138 (12.1) | 187 (18.3) | 102 (20.5) | 103 (22.2) | 173 (24.8) | 120 (24.5) | |
| Richest quintile | 791 (16.8) | 92 (8.4) | 198 (18.0) | 107 (20.3) | 101 (20.4) | 175 (24.4) | 118 (24.6) | |
| Maternal Cognitive Score‡ | 0.0 (1.0) | −0.42 (0.72) | −0.05 (0.96) | 0.06 (0.95) | 0.42 (1.06) | 0.43 (1.10) | 0.52 (1.23) | <0.001 |
| Schooling outcomes | ||||||||
| Key stage 4 (age 16) | ||||||||
| English GCSE | ||||||||
| Failed (marks <4) | 1472 (32.6) | 472 (41.7) | 406 (34.0) | 176 (32.0) | 130 (24.4) | 180 (23.2) | 108 (19.2) | <0.001 |
| Low pass (marks ≥4 and <7) | 2639 (51.5) | 627 (48.7) | 686 (52.5) | 309 (52.9) | 282 (52.6) | 441 (54.1) | 294 (52.3) | |
| High pass (marks ≥7) | 915 (15.9) | 130 (9.6) | 192 (13.5) | 90 (14.9) | 135 (23.0) | 200 (22.7) | 168 (28.5) | |
| Mathematics GCSE | ||||||||
| Failed (marks <4) | 1401 (31.2) | 467 (41.9) | 358 (29.5) | 169 (30.0) | 111 (20.8) | 173 (21.3) | 123 (23.7) | <0.001 |
| Low pass (marks ≥4 and <7) | 2529 (50.0) | 605 (47.1) | 702 (54.8) | 288 (50.7) | 296 (54.8) | 386 (48.8) | 252 (44.9) | |
| High pass (marks ≥7) | 1082 (18.8) | 154 (11.0) | 219 (15.7) | 117 (19.3) | 138 (24.4) | 260 (29.9) | 194 (31.4) | |
| Five GCSE passes (marks≥5)** | 3030 (56.4) | 590 (43.8) | 740 (56.0) | 329 (55.4) | 380 (69.2) | 575 (69.5) | 416 (71.0) | <0.001 |
| Attainment 8 score‡ †† | 47.1 (18.9) | 41.4 (15.3) | 46.5 (18.3) | 47.6 (19.3) | 52.3 (20.1) | 52.9 (20.5) | 54.2 (21.2) | <0.001 |
*Parameters were estimated considering the complex design of the Millennium Cohort Study sample. The counts reflect the absolute number of participants included.
†Χ2 or mean difference, as appropriate.
‡Mean (SD).
§Consumption of ≥3 units per week or ≥3 units per occasion during pregnancy.
¶National Vocational Qualifications (NVQ): NVQ 4 and 5: higher/university education, NVQ3: A-levels, qualifications obtained at age 18, NVQ 1 and 2: qualifications obtained at age 16, at the end of secondary education.
**Five GCSEs passed with marks ≥5, including English and Mathematics.
††Attainment 8 is the additive score of the marks of a student in their best eight GCSEs, including English and Mathematics (double weighted) and can range between 0 and 90.
BF, breastfeeding; GCSE, General Certificate of Secondary Education.