Population characteristics for infants born 22+0–31+6 weeks’ gestation, England 2008–2014, and admitted to a neonatal unit contributing to the National Neonatal Research Database
| 2008 n=6103 | 2009 n=6487 | 2010 n=7386 | 2011 n=7733 | 2012 n=7667 | 2013 n=7367 | 2014 n=7369 | Total n=50 112 | p Value for trend | ||
| n (%) | n (%) | n (%) | n (%) | n (%) | n (%) | n (%) | n (%) | |||
| Gestational age (complete weeks) | 22+0–22+6 | 14 (0.2) | 9 (0.1) | 11 (0.1) | 9 (0.1) | 5 (0.1) | 12 (0.2) | 8 (0.1) | 68 (0.1) | p<0.01 |
| 23+0–23+6 | 181(3) | 151 (2.3) | 187 (2.5) | 156(2) | 200 (2.6) | 186 (2.5) | 220(3) | 1281 (2.6) | ||
| 24+0–24+6 | 356 (5.8) | 332 (5.1) | 358 (4.8) | 434 (5.6) | 406 (5.3) | 384 (5.2) | 374 (5.1) | 2644 (5.3) | ||
| 25+0–25+6 | 404 (6.6) | 362 (5.6) | 401 (5.4) | 456 (5.9) | 466 (6.1) | 458 (6.2) | 446 (6.1) | 2993(6) | ||
| 26+0–26+6 | 521 (8.5) | 516(8) | 589(8) | 648 (8.4) | 587 (7.7) | 567 (7.7) | 590(8) | 4018(8) | ||
| 27+0–27+6 | 600 (9.8) | 703 (10.8) | 717 (9.7) | 753 (9.7) | 786 (10.3) | 671 (9.1) | 642 (8.7) | 4872 (9.7) | ||
| 28+0–28+6 | 755 (12.4) | 828 (12.8) | 966 (13.1) | 964 (12.5) | 925 (12.1) | 913 (12.4) | 895 (12.1) | 6246 (12.5) | ||
| 29+0–29+6 | 855(14) | 906(14) | 1063 (14.4) | 1100 (14.2) | 1067 (13.9) | 1084 (14.7) | 1030(14) | 7105 (14.2) | ||
| 30+0–30+6 | 1072 (17.6) | 1145 (17.7) | 1318 (17.8) | 1361 (17.6) | 1349 (17.6) | 1334 (18.1) | 1365 (18.5) | 8944 (17.8) | ||
| 31+0–31+6 | 1345(22) | 1535 (23.7) | 1776(24) | 1852 (23.9) | 1876 (24.5) | 1758 (23.9) | 1799 (24.4) | 11 941 (23.8) | ||
| Birth weight (g) | <500 | 53 (0.9) | 47 (0.7) | 45 (0.6) | 40 (0.5) | 52 (0.7) | 74 (1.0) | 71 (1.0) | 382 (0.8) | p=0.74 |
| 500–999 | 2053 (33.6) | 2061 (31.8) | 2286(31) | 2523 (32.6) | 2446 (31.9) | 2332 (31.7) | 2360(32) | 16 061 (32.1) | ||
| 1000–1499 | 2519 (41.3) | 2811 (43.3) | 3209 (43.4) | 3310 (42.8) | 3297(43) | 3148 (42.7) | 3160 (42.9) | 21 454 (42.8) | ||
| 1500–1999 | 1358 (22.3) | 1472 (22.7) | 1716 (23.2) | 1737 (22.5) | 1757 (22.9) | 1700 (23.1) | 1667 (22.6) | 11 407 (22.8) | ||
| ≥2000 | 120 (2.0) | 96 (1.5) | 130 (1.8) | 123 (1.6) | 115 (1.5) | 113 (1.5) | 111 (1.5) | 808 (1.6) | ||
| Small-for-gestational age | No | 5211 (85.4) | 5530 (85.2) | 6305 (85.4) | 6540 (84.6) | 6569 (85.7) | 6271 (85.1) | 6261 (85.0) | 42 687 (85.2) | p=0.62 |
| Yes | 892 (14.6) | 957 (14.8) | 1081 (14.6) | 1193 (15.4) | 1098 (14.3) | 1096 (14.9) | 1108 (15.0) | 7425 (14.8) | ||
| Sex | Female | 2831 (46.4) | 3099 (47.8) | 3367 (45.6) | 3547 (45.9) | 3513 (45.8) | 3278 (44.5) | 3376 (45.8) | 23 011 (45.9) | p=0.01 |
| Male | 3272 (53.6) | 3388 (52.2) | 4019 (54.4) | 4186 (54.1) | 4154 (54.2) | 4089 (55.5) | 3993 (54.2) | 27 101 (54.1) | ||
| Multiplicity of pregnancy | Singleton | 4456 (73) | 4714 (72.7) | 5364 (72.6) | 5628 (72.8) | 5609 (73.2) | 5522 (75.0) | 5416 (73.5) | 36 709 (73.3) | p=0.02 |
| Twins | 1514 (24.8) | 1626 (25.1) | 1828 (24.7) | 1889 (24.4) | 1852 (24.2) | 1675 (22.7) | 1777 (24.1) | 12 161 (24.3) | ||
| Triplets+ | 133 (2.2) | 147 (2.3) | 194 (2.6) | 216 (2.8) | 206 (2.7) | 170 (2.3) | 176 (2.4) | 1242 (2.5) | ||
| Any antenatal steroids given | No | 738 (12.6) | 728 (11.5) | 868 (12.1) | 864 (11.4) | 879 (11.6) | 773 (10.6) | 766 (10.4) | 5616 (11.4) | p<0.01 |
| Yes | 5137 (87.4) | 5585 (88.5) | 6312 (87.9) | 6724 (88.6) | 6704 (88.4) | 6552 (89.4) | 6579 (89.6) | 43 593 (88.6) | ||
| Missing | 228 | 174 | 206 | 145 | 84 | 42 | 24 | 903 | ||
| Mode of delivery | Vaginal | 2344 (45.2) | 2557 (44.1) | 2949 (43.6) | 3080 (43.1) | 3001 (42.6) | 2848 (42.2) | 2793 (41.1) | 19 572 (43.0) | p<0.01 |
| Caesarean | 2843 (54.8) | 3246 (55.9) | 3817 (56.4) | 4070 (56.9) | 4044 (57.4) | 3896 (57.8) | 3996 (58.9) | 25 912 (57.0) | ||
| Missing | 916 | 684 | 620 | 583 | 622 | 623 | 580 | 4626 | ||
| Maternal age | <20 | 531 (8.9) | 520 (8.1) | 630 (8.6) | 581 (7.5) | 527 (6.9) | 469 (6.4) | 450 (6.2) | 3708 (7.5) | p<0.01 |
| 20–24 | 1088 (18.3) | 1201 (18.6) | 1342 (18.2) | 1498 (19.4) | 1390 (18.2) | 1248 (17.0) | 1175 (16.1) | 8942 (18.0) | ||
| 25–29 | 1526 (25.7) | 1658 (25.7) | 1900 (25.8) | 1984 (25.7) | 1986 (26.0) | 1892 (25.8) | 1934 (26.5) | 12 880 (25.9) | ||
| 30–34 | 1499 (25.2) | 1721 (26.7) | 1962 (26.7) | 2072 (26.9) | 2123 (27.8) | 2085 (28.5) | 2165 (29.6) | 13 627 (27.4) | ||
| 35–40 | 1023 (17.2) | 1063 (16.5) | 1206 (16.4) | 1235 (16.0) | 1216 (15.9) | 1245 (17.0) | 1192 (16.3) | 8180 (16.5) | ||
| >40 | 270 (4.5) | 290 (4.5) | 321 (4.4) | 335 (4.3) | 396 (5.2) | 389 (5.3) | 386 (5.3) | 2387 (4.8) | ||
| Missing | 166 | 34 | 25 | 28 | 29 | 39 | 67 | 388 |
Percentages are of the total non-missing values. p Value from non-parametric trend test.