Table 2. Demographic characteristics according to birth weight categories.
| Birth weight ≥ 2,500 g (n = 9,586,744) | Low birth weight (n = 606,800) | Very low birth weight (n = 97,246) | Birth weight missing (n = 45,406) | |
|---|---|---|---|---|
| Maternal age (years) | ||||
| <20 | 632,058 (6.6) | 56,372 (9.3) | 8,999 (9.3) | 2,821 (6.2) |
| 20–24 | 1,785,158 (18.6) | 133,010 (21.9) | 19,669 (20.2) | 8,491 (18.7) |
| 25–29 | 2,697,989 (28.1) | 163,814 (27.0) | 25,485 (26.2) | 12,344 (27.2) |
| 30–34 | 2,791,293 (29.1) | 150,470 (24.8) | 24,480 (25.2) | 12,637 (27.9) |
| 35–39 | 1,397,224 (14.6) | 82,428 (13.6) | 14,705 (15.1) | 7,375 (16.3) |
| ≥40 | 283,019 (3.0) | 20,706 (3.4) | 3,908 (4.0) | 1,691 (3.7) |
| Missing | 4 (0.0) | 0 (0.0) | 0 (0.0) | 47 (0.1) |
| Parity | ||||
| 0 | 2,271,216 (40.0) | 156,788 (50.1) | 24,541 (50.2) | 13,495 (52.6) |
| 1 | 2,095,213 (36.9) | 86,370 (27.6) | 13,165 (26.9) | 7,098 (27.7) |
| 2 | 841,217 (14.8) | 40,002 (12.8) | 6,282 (12.9) | 3,093 (12.1) |
| ≥3 | 465,144 (8.2) | 29,492 (9.4) | 4,875 (10.0) | 1,956 (7.6) |
| Missing | 3,913,954 (40.8) | 294,148 (48.5) | 48,383 (49.8) | 19,800 (43.6) |
| Marital status | ||||
| Married | 5,672,849 (59.2) | 312,659 (51.5) | 48,865 (50.2) | 25,614 (56.4) |
| Not married | 3,913,895 (40.8) | 294,141 (48.5) | 48,381 (49.8) | 19,792 (43.6) |
| Missing | 0 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0) |
| Sex | ||||
| Male | 4,939,679 (51.5) | 288,753 (47.6) | 49,784 (51.2) | 23,314 (51.3) |
| Female | 4,647,062 (48.5) | 318,047 (52.4) | 47,462 (48.8) | 22,092 (48.7) |
| Missing | 3 (0.0) | 0 (0.0) | 0 (0.0) | 0 (0) |
| IMD quintile | ||||
| 1 (most deprived) | 1,676,895 (18.0) | 129,769 (21.7) | 21,871 (22.8) | 11,085 (26.4) |
| 2 | 2,439,576 (26.1) | 168,089 (28.0) | 27,599 (28.8) | 11,233 (26.8) |
| 3 | 2,100,475 (22.5) | 132,485 (22.1) | 21,227 (22.1) | 8,373 (20.0) |
| 4 | 1,842,889 (19.7) | 102,493 (17.1) | 15,510 (16.1) | 7,647 (18.2) |
| 5 (least deprived) | 1,274,139 (13.7) | 66,542 (11.0) | 9,692 (10.1) | 3,614 (8.6) |
| Missing | 252,770 (2.6) | 7,422 (1.2) | 1,347 (1.4) | 3,454 (7.6) |
| Region | ||||
| Greater London | 1,754,925 (18.8) | 120,352 (20.1) | 21,381 (22.3) | 16,463 (39.2) |
| North East | 440,830 (4.7) | 29,295 (4.9) | 4,579 (4.8) | 1,494 (3.6) |
| North West | 1,265,206 (13.6) | 85,422 (14.3) | 13,108 (13.7) | 4,762 (11.4) |
| Yorkshire and the Humber | 932,580 (10.0) | 64,903 (10.8) | 9,851 (10.7) | 3,195 (7.6) |
| East Midlands | 680,606 (7.3) | 45,086 (7.5) | 6,932 (7.2) | 1,160 (2.8) |
| West Midlands | 1,020,237 (10.9) | 75,470 (12.6) | 12,132 (12.7) | 2,025 (4.8) |
| East of England | 969,400 (10.4) | 54,056 (9.0) | 8,422 (8.8) | 3,096 (7.4) |
| South East | 769,979 (8.2) | 40,383 (6.7) | 5,996 (6.3) | 2,407 (5.7) |
| South Central | 680,340 (7.3) | 38,901 (6.5) | 6,345 (6.6) | 2,327 (5.5) |
| South West | 819,871 (8.8) | 45,510 (7.6) | 7,153 (7.5) | 5,023 (12.0) |
| Missing | 252,770 (2.6) | 7,422 (1.2) | 1,347 (1.4) | 3,454 (7.6) |
| Urbanisation level | ||||
| Urban | 9,128,455 (97.4) | 589,290 (98.3) | 94,414 (98.6) | 41,391 (98.7) |
| Rural | 205,519 (2.6) | 10,088 (1.7) | 1,485 (1.4) | 561 (1.3) |
| Missing | 252,770 (2.6) | 7,422 (1.2) | 1,347 (1.4) | 3,454 (7.6) |
Numbers represent numbers of live-born babies in each stratum. Percentages in parentheses relate to all babies with valid data for that particular variable. For missing data, percentages of the full sample are given. IMD = Index of Multiple Deprivation.