Table 1.
Univariate analysis of risk factors associated with stillbirths compared with live births
| Risk factors | No (%) of all births | No (%) of stillbirths | Rate/1000 births | Relative risk (95% CI) |
|---|---|---|---|---|
| Total | 92 218 (100) | 389 (100) | 4.2 | — |
| General maternal characteristics | ||||
| Age (years): | n=92 208 | n=389 | ||
| <20 | 6456 (7.0) | 33 (8.5) | 5.1 | 1.3 (0.9 to 1.9) |
| 20-24 | 20 834 (22.6) | 99 (25.5) | 4.8 | 1.2 (0.9 to 1.6) |
| 25-30 | 27 110 (29.4) | 107 (27.5) | 3.9 | Reference |
| 30-34 | 23 110 (25.1) | 79 (20.3) | 3.4 | 0.9 (0.6 to 1.2) |
| ≥35 | 14 698 (15.9) | 71 (18.3) | 4.8 | 1.2 (0.9 to 1.6) |
| Parity: | n=91 160 | n=377 | ||
| 0 | 38 653 (42.4) | 192 (50.9) | 5.0 | 1.9 (1.4 to 2.4) |
| 1 | 29 791 (32.7) | 79 (21.0) | 2.7 | Reference |
| 2 | 13 421 (14.7) | 56 (14.9) | 4.2 | 1.6 (1.1 to 2.2) |
| ≥3 | 9295 (10.2) | 50 (13.3) | 5.4 | 2.0 (1.4 to 2.9) |
| Body mass index: | n=90 350 | n=389 | ||
| <18.5 | 3109 (3.4) | 12 (3.1) | 3.9 | 1.0 (0.5 to 1.8) |
| 18.5-24.9 | 43 898 (48.6) | 173 (44.5) | 3.9 | Reference |
| 25-29.9 | 25 156 (27.8) | 101 (26.0) | 4.0 | 1.0 (0.8 to 1.3) |
| 30-34.9 | 11 427 (12.6) | 61 (15.7) | 5.3 | 1.4 (1.0 to 1.8) |
| ≥35 | 6760 (7.5) | 42 (10.8) | 6.2 | 1.6 (1.1 to 2.2) |
| Maternal ethnic origin: | n=87 911 | n=334 | ||
| European: | ||||
| UK | 60 130 (67.9) | 192 (57.5) | 3.2 | Reference |
| Non-UK | 4254 (4.8) | 17 (5.1) | 4.0 | 1.3 (0.8 to 2.1) |
| African* | 2986 (3.2) | 22 (5.7) | 7.4 | 2.3 (1.5 to 3.6) |
| African-Caribbean* | 1796 (2.0) | 12 (3.1) | 6.7 | 2.1 (1.2 to 3.7) |
| Bangladeshi* | 1674 (1.8) | 7 (1.8) | 4.2 | 1.3 (0.6 to 2.8) |
| Indian: | ||||
| UK | 2282 (2.6) | 9 (2.7) | 3.9 | 1.2 (0.6 to 2.4) |
| Non-UK | 2189 (2.5) | 14 (4.2) | 6.4 | 2.0 (1.2 to 3.4) |
| Pakistani: | ||||
| UK | 3412 (3.9) | 14 (4.2) | 4.1 | 1.3 (0.7 to 2.2) |
| Non-UK | 4378 (4.9) | 30 (9.0) | 6.9 | 2.1 (1.5 to 3.1) |
| Other: | ||||
| UK | 1535 (1.7) | 6 (1.8) | 3.9 | 1.2 (0.5 to 2.8) |
| Non-UK | 3275 (3.7) | 11 (3.3) | 3.4 | 1.1 (0.6 to 1.9) |
| Place of birth: | n=88 559 | n=334 | ||
| UK | 69 878 (78.9) | 236 (70.7) | 3.4 | Reference |
| Other | 18 681 (21.1) | 98 (29.3) | 5.2 | 1.6 (1.3 to 2.1) |
| Social factors | ||||
| Mother not employed: | n=86 969 | n=330 | ||
| No | 50 905 (58.5) | 176 (53.3) | 3.5 | Reference |
| Yes | 36 064 (41.5) | 154 (46.7) | 4.3 | 1.2 (1.0 to 1.5) |
| Partner not employed: | n=81 624 | n=310 | ||
| No | 63 212 (77.4) | 230 (74.2) | 3.6 | Reference |
| Yes | 11 950 (14.6) | 58 (18.7) | 4.9 | 1.3 (1.0 to 1.8) |
| No partner | 6462 (7.9) | 22 (7.1) | 3.4 | 0.9 (0.6 to 1.4) |
| Baby’s father blood relation: | n=81 627 | n=298 | ||
| No | 76 084 (93.2) | 273 (91.6) | 3.6 | Reference |
| Yes | 5543 (6.8) | 25 (8.4) | 4.5 | 1.3 (0.8 to 1.9) |
| Index of multiple deprivation (fifths): | n=92 218 | n=389 | ||
| 1-3 (least deprived) | 34 863 (37.8) | 115 (29.6) | 3.3 | Reference |
| 4 | 19 230 (20.9) | 69 (17.7) | 3.6 | 1.1 (0.8 to 1.5) |
| 5 (most deprived) | 38 125 (41.3) | 205 (52.7) | 5.4 | 1.6 (1.3 to 2.0) |
| Maternal history | ||||
| Mental health problems: | n=89 985 | n=340 | ||
| No | 79 553 (88.4) | 285 (83.8) | 3.6 | Reference |
| Yes | 10 432 (11.6) | 55 (16.2) | 5.3 | 1.5 (1.1 to 2.0) |
| Pre-existing hypertension: | n=90 965 | n=342 | ||
| No | 88 528 (97.3) | 329 (96.2) | 3.7 | Reference |
| Yes | 2437 (2.7) | 13 (3.8) | 5.3 | 1.4 (0.8 to 2.5) |
| Pre-existing diabetes: | n=90 965 | n=342 | ||
| No | 90 238 (99.2) | 332 (97.1) | 3.7 | Reference |
| Yes | 727 (0.8) | 10 (2.9) | 13.8 | 3.7 (2.0 to 6.9) |
| Cardiac disease: | n=90 965 | n=342 | ||
| No | 89 051 (97.9) | 331 (96.8) | 3.7 | Reference |
| Yes | 1914 (2.1) | 11 (3.2) | 5.7 | 1.5 (0.8 to 2.8) |
| Previous stillbirth para ≥1 (n=53 565): | n=52 475 | n=184 | ||
| No | 51 482 (98.1) | 173 (94.0) | 3.4 | Reference |
| Yes | 993 (1.9) | 11 (6.0) | 11.1 | 3.3 (1.8 to 6.0) |
| Pregnancy related factors | ||||
| Smoking in pregnancy: | n=85 337 | n=333 | ||
| Non-smoker | 52 473 (61.5) | 166 (49.8) | 3.2 | Reference |
| Smoker | 17 834 (20.9) | 104 (31.2) | 5.8 | 1.8 (1.4 to 2.3) |
| Passive smoker | 15 030 (17.6) | 63 (18.9) | 4.2 | 1.3 (1.0 to 1.8) |
| Alcohol consumption: | n=88 569 | n=329 | ||
| No | 81 288 (91.8) | 305 (92.7) | 3.8 | Reference |
| Yes | 7281 (8.2) | 24 (7.3) | 3.3 | 0.9 (0.6 to 1.3) |
| Antenatal folic acid: | n=88 173 | n=326 | ||
| Yes | 74 526 (84.5) | 262 (80.4) | 3.5 | Reference |
| No | 13 647 (15.5) | 64 (19.6) | 4.7 | 1.3 (1.0 to 1.8) |
| Late booking (≥13 weeks): | n=89 886 | n=338 | ||
| No | 74 644 (83.0) | 269 (79.6) | 3.6 | Reference |
| Yes | 15 242 (17.0) | 69 (20.4) | 4.5 | 1.3 (1.0 to 1.6) |
| Complications in pregnancy | ||||
| Gestational diabetes: | n=91 010 | n=339 | ||
| No | 88 134 (96.8) | 326 (96.2) | 3.7 | Reference |
| Yes | 2876 (3.2) | 13 (3.8) | 4.5 | 1.2 (0.7 to 2.1) |
| Pregnancy induced hypertension: | n=91 010 | n=339 | ||
| No | 86 640 (95.2) | 322 (95.0) | 3.7 | Reference |
| Yes | 4370 (4.8) | 17 (5.0) | 3.9 | 1.0 (0.6 to 1.7) |
| Pre-eclampsia: | n=91 010 | n=339 | ||
| No | 89 938 (98.8) | 328 (96.8) | 3.6 | Reference |
| Yes | 1072 (1.2) | 11 (3.2) | 10.3 | 2.8 (1.5 to 5.1) |
| Antepartum haemorrhage: | n=91 010 | n=339 | ||
| No | 83 902 (92.2) | 277 (81.7) | 3.3 | Reference |
| Yes | 7108 (7.8) | 62 (18.3) | 8.7 | 2.6 (2.0 to 3.5) |
| Fetal/neonatal characteristics | ||||
| Sex: | n=92 136 | n=383 | ||
| Boy | 47 308 (51.3) | 209 (54.6) | 4.4 | Reference |
| Girl | 44 828 (48.7) | 174 (45.4) | 3.9 | 0.9 (0.7 to 1.1) |
| Gestational age at delivery | n=92 218 | n=389 | ||
| Median (interquartile range) days | 280 (272-286) | 240 (198-271) | ||
| Birth weight (g): | n=91 858 | n=389 | ||
| Mean (SD) | 3343.3 (569.1) | 1931.6 (1146.2) | ||
| Gestation related optimal weight centile: | n=88 053 | n= 380 | ||
| Median (interquartile range) | 41.5 (19.5-67.5) | 9.7 (0.6-37.3) | ||
| ≤10 | 69 840 (75.7) | 168 (43.2) | 16.7 | 6.8 (5.6 to 8.4) |
| 10-90 | 11 697 (12.7) | 195 (50.1) | 2.4 | Reference |
| >90 | 6516 (7.1) | 17 (4.4) | 2.6 | 1.1 (0.7 to 1.8) |
| Fetal growth restriction†: | n=88 053 | n=380 | ||
| No | 76 356 (86.7) | 185 (48.7) | 2.4 | Reference |
| Yes | ||||
| Detected antenatally | 3601 (4.1) | 35 (9.2) | 9.7 | 4.0 (2.8 to 5.7) |
| Not detected antenatally | 8096 (9.2) | 160 (42.1) | 19.8 | 8.0 (6.5 to 9.9) |
*Place of birth combined if either subgroup <1000 women.
†Birth weight <10th gestation related optimal weight centile.