Descriptive statistics by maternal BMI for the main analysis cohort (N=9540)
| Total (N=9540) | Underweight (n=489) | Healthy weight (n=3687) | Overweight (n=2886) | Obese grade 1 (n=1520) | Obese grade 2 and 3 (n=958) | |
| Mother’s age | ||||||
| <25 | 3037 (32) | 284 (58) | 1443 (39) | 747 (26) | 348 (23) | 215 (22) |
| 25–29 | 3108 (33) | 137 (28) | 1196 (32) | 994 (35) | 481 (32) | 300 (31) |
| 30–34 | 2208 (23) | 56 (12) | 735 (20) | 734 (25) | 423 (28) | 260 (27) |
| 35+ | 1187 (12) | 12 (2) | 313 (9) | 411 (14) | 268 (18) | 183 (19) |
| Child sex | ||||||
| Male | 4828 (51) | 242 (50) | 1776 (49) | 1424 (50) | 743 (49) | 430 (45) |
| Female | 4615 (49) | 242 (50) | 1859 (51) | 1445 (50) | 762 (51) | 520 (55) |
| Parity | ||||||
| Nulliparous | 3773 (42) | 285 (60) | 1779 (51) | 1040 (38) | 430 (30) | 239 (26) |
| Parous | 5306 (58) | 188 (40) | 1734 (49) | 1700 (62) | 1016 (70) | 668 (74) |
| Socioeconomic position | ||||||
| Least deprived and most educated | 1760 (20) | 79 (19) | 735 (22) | 577 (22) | 248 (17) | 121 (13) |
| Employed, not materially deprived | 1802 (21) | 47 (11) | 762 (23) | 551 (21) | 285 (20) | 157 (17) |
| Employed, no access to money | 1317 (15) | 52 (12) | 454 (14) | 429 (16) | 235 (17) | 147 (16) |
| Benefits but coping | 2455 (28) | 172 (41) | 859 (26) | 733 (28) | 412 (29) | 279 (31) |
| Most deprived | 1346 (16) | 72 (17) | 465 (14) | 362 (14) | 244 (17) | 203 (22) |
| Maternal education | ||||||
| <GCSE | 1793 (21) | 91 (22) | 644 (20) | 518 (20) | 295 (21) | 245 (28) |
| GCSE A-level | 3982 (46) | 202 (48) | 1477 (45) | 1191 (45) | 675 (48) | 437 (49) |
| >GCSE A-level | 2279 (27) | 110 (26) | 938 (29) | 739 (28) | 340 (24) | 152 (17) |
| Other | 553 (6) | 18 (4) | 197 (6) | 173 (7) | 101 (7) | 64 (7) |
| IMD score (quintiles) | ||||||
| Q1 | 3197 (37) | 193 (46) | 1125 (34) | 934 (35) | 560 (39) | 385 (42) |
| Q2 | 2325 (27) | 132 (31) | 845 (26) | 702 (26) | 412 (29) | 234 (26) |
| Q3 | 1696 (20) | 61 (14) | 671 (20) | 536 (20) | 254 (18) | 174 (19) |
| Q4 | 1184 (14) | 34 (8) | 516 (16) | 377 (14) | 157 (11) | 100 (11) |
| Q5 | 317 (4) | <10 (1) | 142 (4) | 109 (4) | 44 (3) | 18 (2) |
| Ethnicity | ||||||
| White, British | 3742 (40) | 107 (22) | 1641 (45) | 1067 (38) | 511 (34) | 416 (44) |
| Pakistani | 4196 (45) | 272 (57) | 1341 (37) | 1359 (48) | 797 (53) | 427 (45) |
| Other | 1463 (15) | 102 (21) | 633 (18) | 420 (15) | 202 (13) | 106 (11) |
| Smoked during pregnancy | ||||||
| Yes | 1439 (13) | 72 (17) | 629 (19) | 406 (15) | 169 (12) | 163 (18) |
| No | 7277 (83) | 353 (83) | 2667 (81) | 2250 (85) | 1258 (88) | 749 (82) |
| Child BMI (4–5 years) | ||||||
| Underweight | 324 (5) | 52 (15) | 133 (5) | 83 (4) | 41 (4) | 15 (2) |
| Healthy weight | 5261 (80) | 273 (80) | 2114 (84) | 1642 (81) | 800 (76) | 432 (69) |
| Overweight | 659 (10) | 11 (3) | 193 (8) | 214 (11) | 130 (12) | 111 (18) |
| Obese | 322 (5) | <10 (2) | 75 (3) | 85 (4) | 84 (8) | 71 (11) |
| Gestational age | ||||||
| <34 weeks | 131 (1) | <10 (2) | 44 (1) | 43 (1) | 16 (1) | 19 (2) |
| 34–36 weeks | 368 (4) | 29 (6) | 141 (4) | 93 (3) | 61 (4) | 44 (5) |
| 37–38 weeks | 1995 (21) | 115 (24) | 688 (19) | 594 (21) | 366 (24) | 232 (24) |
| 39+ weeks | 6949 (74) | 331 (68) | 2762 (76) | 2139 (75) | 1062 (71) | 655 (69) |
| Mode of birth | ||||||
| Vaginal | 7280 (77) | 425 (88) | 2957 (81) | 2192 (76) | 1102 (73) | 604 (64) |
| Caesarean section | 2163 (23) | 59 (12) | 678 (19) | 677 (24) | 403 (27) | 346 (36) |
| Breastfeeding | ||||||
| Never | 702 (11) | 39 (12) | 243 (10) | 199 (10) | 119 (11) | 102 (17) |
| <6 weeks | 1847 (28) | 98 (31) | 726 (29) | 557 (27) | 286 (27) | 180 (30) |
| ≥6 weeks | 3971 (61) | 184 (57) | 1522 (61) | 1296 (63) | 649 (62) | 320 (53) |
| Vaccination status at 1 year | ||||||
| Fully vaccinated | 8328 (89) | 434 (90) | 3189 (89) | 2527 (89) | 1343 (90) | 835 (89) |
| Partially vaccinated | 470 (5) | 22 (5) | 189 (5) | 131 (5) | 78 (5) | 50 (5) |
| Not vaccinated | 535 (6) | 25 (5) | 214 (6) | 170 (6) | 70 (5) | 56 (6) |
| High-risk pregnancy | ||||||
| No | 7852 (82) | 455 (6) | 3286 (42) | 2387 (30) | 1106 (14) | 618 (8) |
| Yes | 1688 (18) | 34 (2) | 401 (24) | 499 (30) | 414 (25) | 340 (20) |
Data are shown as n (%).
Low counts are suppressed to <10 in order to avoid unintentional disclosure.
χ2 tests were all p<0.0001, with the exception of child sex (p=0.198) and vaccination status at 1 year (p=0.665).
BMI, body mass index; IMD, Index of Multiple Deprivation.