Table 2.
Participant level characteristics, late stillbirth risk factors, and going-to-sleep position in last two weeks in participating case–control studies and pooled IPD meta-analysis.
| Characteristic | TASS Stacey et al. (2011) [6] |
SSS Gordon et al. (2015) [9] |
MCSS McCowan et al. (2017) [4] |
MiNESS Heazell et al. (2017) [8] |
STARS O'Brien et al. (2018) [7] |
Collaborative Individual Participant Data of Going-to-sleep and Stillbirth (CRIBSS) analysis |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Case | Control | Case | Control | Case | Control | Case | Control | Case | Control | Case | Control | Univariable odds ratio (95% CI) |
Adjusted odds ratio (95% CI) |
|
| Total participants | 155 (33.8) | 304 (66.2) | 103 (34.9) | 192 (65.1) | 163 (22.5) | 560 (77.5) | 288 (28.2) | 733 (71.8) | 142 (23.3) | 468 (76.7) | 851 (27.4) | 2257 (72.6) | Case n = 851 Control n = 2257 Total 3108 |
Case n = 826 Control n = 1953 Total 2779 |
| Age (years) | ||||||||||||||
| < 20 | 10 (6.5) | 24 (7.9) | 3 (2.9) | 1 (0.5) | 9 (5.5) | 17 (3.04) | 7 (2.4) | 15 (2.1) | 9 (6.3) | 21 (4.5) | 38 (4.5) | 78 (3.5) | 1.50 (0.98–2.28) | 1.33 (0.78–2.28) |
| 20–24 | 29 (18.7) | 44 (14.5) | 4 (3.9) | 14 (7.3) | 23 (14.1) | 79 (14.11) | 47 (16.3) | 81 (11.1) | 12 (8.5) | 56 (12.0) | 115 (13.5) | 274 (12.1) | 1.33 (1.02–1.73) | 1.04 (0.74–1.47) |
| 25–29 | 40 (25.8) | 75 (24.7) | 25 (24.3) | 43 (22.4) | 40 (24.5) | 157 (28.04) | 82 (28.5) | 219 (29.9) | 41 (28.9) | 137 (29.3) | 228 (26.8) | 631 (28.0) | 1.12 (0.91–1.38) | 0.98 (0.76–1.26) |
| 30–34 | 44 (28.4) | 92 (30.3) | 39 (37.9) | 66 (34.4) | 48 (29.5) | 191 (34.11) | 85 (29.5) | 268 (36.6) | 49 (34.5) | 177 (37.8) | 265 (31.1) | 794 (35.2) | 1 | 1 |
| 35–39 | 29 (18.7) | 57 (18.8) | 25 (24.3) | 51 (26.6) | 29 (17.8) | 96 (17.14) | 51 (17.7) | 125 (17.1) | 26 (18.3) | 67 (14.3) | 160 (18.8) | 396 (17.6) | 1.19 (0.94–1.51) | 1.23 (0.93–1.62) |
| ≥ 40 | 3 (1.9) | 12 (4.0) | 7 (6.8) | 17 (8.9) | 14 (8.6) | 20 (3.57) | 16 (5.6) | 25 (3.4) | 5 (3.5) | 10 (2.1) | 45 (5.3) | 84 (3.7) | 1.60 (1.08–2.38) | 1.47 (0.93–2.31) |
| Earliest pregnancy BMI (kg/m2) | 27.5 (23.2–33.3) | 25.0 (22.2–30.8) | 23.1 (21.2–28.3) | 22.8 (20.8–26) | 26.6 (23.1–33.5) | 24.8 (22.0–29.6) | 26.1 (22.5–30.3) | 24.9 (22.1–28.8) | 26.8 (22.8–32.5) | 25.2 (22.5–31.1) | 26.0 (22.5–31.4) | 24.8 (22.0–29.3) | 1.04 (1.03–1.05) | 1.03 (1.01–1.05) |
| Ethnicity | ||||||||||||||
| White | 55 (35.5) | 134 (44.1) | 57 (55.3) | 136 (70.8) | 65 (39.9) | 260 (46.4) | 233 (80.9) | 594 (81.0) | 112 (78.9) | 421 (90.0) | 522 (61.3) | 1545 (68.5) | 1 | 1 |
| Black | 4 (2.6) | 1 (0.3) | 1 (1.0) | 3 (1.6) | 2 (1.3) | 3 (0.5) | 12 (4.2) | 29 (4.0) | 3 (2.1) | 6 (1.3) | 22 (2.6) | 42 (1.9) | 1.63 (0.94–2.84) | 1.77 (0.92–3.42) |
| South Asian* | 15 (9.7) | 27 (8.9) | 9 (8.7) | 10 (5.2) | 17 (10.4) | 85 (15.2) | 38 (13.2) | 94 (12.8) | 11 (7.8) | 3 (0.6) | 90 (10.6) | 219 (9.7) | 1.40 (1.04–1.88) | 1.86 (1.32–2.63) |
| South East/East Asian | 12 (7.7) | 25 (8.2) | 15 (14.6) | 18 (9.4) | 12 (7.4) | 64 (11.4) | 1 (0.4) | 4 (0.6) | 0 | 0 | 40 (4.7) | 111 (4.9) | 1.19 (0.8–1.79) | 1.50 (0.94–2.39) |
| Maori | 19 (12.3) | 46 (15.1) | 1 (1.0) | 3 (1.6) | 26 (16.0) | 58 (10.4) | 0 | 0 | 0 | 0 | 46 (5.4) | 107 (4.7) | 1.55 (1.04–2.32) | 1.10 (0.68–1.78) |
| Pacific | 48 (31.0) | 65 (21.4) | 4 (3.9) | 4 (2.1) | 38 (23.3) | 84 (15.0) | 0 | 0 | 1 (0.7) | 1 (0.2) | 91 (10.7) | 154 (6.8) | 2.25 (1.60–3.16) | 1.88 (1.23–2.88) |
| Others | 2 (1.3) | 6 (2.0) | 16 (15.5) | 18 (9.4) | 3 (1.8) | 6 (1.1) | 4 (1.4) | 12 (1.6) | 15 (10.6) | 37 (7.9) | 40 (4.7) | 79 (3.5) | 1.47 (0.97–2.22) | 1.74 (1.06–2.86) |
| Parity | ||||||||||||||
| Nulliparous | 75 (48.4) | 138 (45.4) | 53 (51.5) | 104 (54.2) | 77 (47.2) | 241 (43.0) | 165 (57.3) | 296 (40.4) | 76 (53.5) | 151 (32.3) | 446 (52.4) | 930 (41.2) | 1.77 (1.49–2.11) | 1.70 (1.38–2.09) |
| 1–2 | 56 (36.1) | 138 (45.4) | 35 (34.0) | 83 (43.2) | 66 (40.5) | 283 (50.5) | 91 (31.6) | 386 (52.7) | 44 (31.0) | 220 (47.0) | 292 (34.3) | 1110 (49.2) | 1 | 1 |
| 3–4 | 17 (11.0) | 26 (8.6) | 14 (13.6) | 4 (2.1) | 14 (8.6) | 30 (5.4) | 25 (8.7) | 45 (6.1) | 17 (12.0) | 71 (15.2) | 87 (10.2) | 176 (7.8) | 1.99 (1.48–2.67) | 1.67 (1.15–2.40) |
| ≥ 5 | 7 (4.5) | 2 (0.7) | 1 (1.0) | 1 (0.5) | 6 (3.7) | 6 (1.1) | 7 (2.4) | 6 (0.8) | 5 (3.5) | 26 (5.6) | 26 (3.1) | 41 (1.8) | 2.63 (1.57–4.42) | 2.29 (1.18–4.44) |
| Education | ||||||||||||||
| Primary | 42 (27.1) | 68 (22.4) | 10 (9.7) | 13 (6.8) | 49 (30.1) | 118 (21.07) | 84 (29.2) | 137 (18.7) | 2 (1.4) | 12 (2.6) | 187 (22.0) | 348 (15.4) | 1.88 (1.49–2.38) | 1.39 (1.02–1.88) |
| Secondary | 48 (31.0) | 73 (24.0) | 24 (23.3) | 33 (17.2) | 18 (11.0) | 63 (11.25) | 40 (13.9) | 84 (11.5) | 31 (21.8) | 90 (19.2) | 161 (18.9) | 343 (15.2) | 1.49 (1.18–1.89) | 1.22 (0.91–1.64) |
| University | 40 (25.8) | 103 (33.9) | 60 (58.3) | 143 (74.5) | 73 (44.8) | 318 (56.79) | 85 (29.5) | 292 (39.8) | 70 (49.3) | 213 (45.5) | 328 (38.5) | 1069 (47.4) | 1 | 1 |
| Post–graduate degree | 0 | 0 | 0 | 0 | 2 (1.2) | 6 (1.07) | 37 (12.9) | 106 (14.5) | 34 (23.9) | 128 (27.4) | 73 (8.6) | 240 (10.6) | 1.00 (0.73–1.37) | 1.13 (0.78–1.64) |
| Non–university trade | 25 (16.1) | 60 (19.7) | 2 (1.9) | 1 (0.5) | 20 (12.3) | 52 (9.29) | 41 (14.2) | 114 (15.6) | 5 (3.5) | 22 (4.7) | 93 (10.9) | 249 (11.0) | 1.30 (0.98–1.72) | 1.14 (0.81–1.59) |
| Marital status | ||||||||||||||
| Single | 17 (11.0) | 23 (7.6) | 8 (7.8) | 7 (3.7) | 20 (12.3) | 29 (5.18) | 40 (13.9) | 71 (9.7) | 7 (4.9) | 13 (2.8) | 92 (10.8) | 143 (6.3) | 1.90 (1.43–2.52) | 1.29 (0.91–1.84) |
| Married/cohabitating | 138 (89.0) | 281 (92.4) | 91 (88.4) | 183 (95.3) | 143 (87.7) | 531 (94.82) | 248 (86.1) | 662 (90.3) | 135 (95.1) | 455 (97.2) | 755 (88.7) | 2112 (93.6) | 1 | 1 |
| Pre-existing hypertension or diabetes | ||||||||||||||
| No | 152 (98.1) | 300 (98.7) | 101 (98.1) | 191 (99.5) | 158 (96.9) | 549 (98.04) | 272 (94.4) | 728 (99.3) | 140 (98.6) | 454 (97.0) | 823 (96.7) | 2222 (98.5) | 1 | 1 |
| Yes | 3 (1.9) | 4 (1.3) | 2 (1.9) | 1 (0.5) | 5 (3.1) | 11 (1.96) | 16 (5.6) | 5 (0.7) | 2 (1.4) | 14 (3) | 28 (3.3) | 35 (1.6) | 2.03 (1.21–3.41) | 1.86 (0.97–3.58) |
| Maternal smoking | ||||||||||||||
| Smoking (beyond first trimester) | 34 (21.9) | 47 (15.5) | 10 (9.7) | 18 (9.4) | 25 (15.3) | 40 (7.1) | 67 (23.3) | 79 (10.8) | 9 (6.3) | 21 (4.5) | 145 (17.0) | 205 (9.1) | 2.05 (1.61–2.6) | 1.62 (1.18–2.23) |
| Non–smoker | 121 (78.1) | 257 (84.5) | 93 (90.3) | 174 (90.6) | 138 (84.7) | 520 (92.9) | 221 (76.7) | 654 (89.2) | 130 (91.6) | 437 (93.4) | 703 (72.6) | 2042 (90.5) | 1 | 1 |
| Recreational drug use (during pregnancy) | ||||||||||||||
| No | 142 (91.6) | 292 (96.1) | 100 (97.1) | 188 (97.9) | 160 (98.2) | 549 (98.0) | 280 (97.2) | 727 (99.2) | 138 (97.2) | 436 (93.7) | 820 (96.4) | 2192 (97.1) | 1 | 1 |
| Yes | 13 (8.4) | 12 (4.0) | 3 (2.9) | 4 (2.1) | 3 (1.8) | 11 (2.0) | 8 (2.8) | 6 (0.8) | 2 (1.4) | 18 (3.9) | 29 (3.4) | 51 (2.3) | 1.49 (0.93–2.38) | 1.15 (0.64–2.06) |
| Infant birthweight customised centile | ||||||||||||||
| < 10th | 56 (36.1) | 27 (8.9) | 21 (20.4) | 15 (7.8) | 42 (25.8) | 67 (12.0) | 118 (41.0) | 82 (11.2) | 41 (28.9) | 21 (4.5) | 278 (32.7) | 212 (9.4) | 5.70 (4.14–7.83) | 5.14 (3.61–7.31) |
| 10–24.9th | 21 (13.6) | 42 (13.8) | 20 (19.4) | 29 (15.1) | 26 (16.0) | 77 (13.8) | 43 (14.9) | 121 (16.5) | 24 (16.9) | 25 (5.3) | 134 (15.8) | 294 (13.0) | 1.89 (1.36–2.64) | 1.82 (1.26–2.63) |
| 25–49.9th | 31 (20.0) | 77 (25.3) | 18 (17.5) | 49 (25.5) | 34 (20.9) | 136 (24.3) | 55 (19.1) | 193 (26.3) | 23 (16.2) | 58 (12.4) | 161 (18.9) | 513 (22.7) | 1.36 (0.99–1.86) | 1.49 (1.06–2.11) |
| 50–74.9th | 20 (12.9) | 79 (26.0) | 14 (13.6) | 60 (31.6) | 35 (21.5) | 132 (23.6) | 43 (14.9) | 153 (20.9) | 15 (10.6) | 58 (12.4) | 127 (14.9) | 482 (21.4) | 1.14 (0.82–1.57) | 1.28 (0.9–1.83) |
| 75–89.9th | 13 (8.4) | 44 (14.5) | 14 (13.6) | 21 (10.9) | 11 (6.8) | 100 (17.9) | 18 (6.3) | 110 (15.0) | 18 (12.7) | 41 (8.8) | 74 (8.7) | 316 (14.0) | 1 | 1 |
| ≥ 90th | 14 (9.0) | 27 (8.9) | 16 (15.5) | 18 (9.4) | 15 (9.2) | 48 (8.6) | 10 (3.5) | 71 (9.7) | 18 (12.7) | 26 (5.6) | 73 (8.6) | 190 (8.4) | 1.58 (1.09–2.31) | 1.57 (1.03–2.38) |
| Going-to-sleep position (last two weeks) | ||||||||||||||
| Left side | 42 (27.1) | 129 (42.4) | 32 (31.1) | 48 (25.0) | 78 (47.9) | 324 (57.9) | 138 (47.9) | 383 (52.3) | 69 (48.6) | 190 (40.6) | 359 (42.2) | 1074 (47.6) | 1 | 1 |
| Supine | 15 (9.7) | 14 (4.6) | 10 (9.7) | 4 (2.1) | 19 (11.7) | 20 (3.6) | 19 (6.6) | 24 (3.3) | 4 (2.8) | 11 (2.4) | 67 (7.9) | 73 (3.2) | 2.89 (2.01–4.14) | 2.63 (1.72–4.04) |
| Right side | 49 (31.6) | 83 (27.3) | 14 (13.6) | 25 (13.0) | 43 (26.4) | 186 (33.2) | 72 (25.0) | 220 (30.0) | 43 (30.3) | 110 (23.5) | 221 (26.0) | 624 (27.7) | 1.10 (0.90–1.34) | 1.04 (0.83–1.31) |
| Prone | 0 | 0 | 0 | 0 | 0 | 0 | 3 (1.0) | 4 (0.6) | 0 (0.0) | 4 (0.9) | 3 (0.4) | 8 (0.4) | 1.15 (0.30–4.45) | 0.63 (0.12–3.25) |
| Variable sides | 9 (5.8) | 23 (7.6) | 38 (36.9) | 110 (57.3) | 14 (8.59) | 20 (3.57) | 32 (11.1) | 76 (10.4) | 9 (6.3) | 36 (7.7) | 102 (12.0) | 265 (11.7) | 0.92 (0.69–1.23) | 0.97 (0.70–1.35) |
| Propped up | 4 (2.6) | 7 (2.3) | 0 | 0 | 4 (2.45) | 9 (1.61) | 9 (3.1) | 15 (2.1) | 3 (2.1) | 15 (3.2) | 20 (2.4) | 46 (2.0) | 1.28 (0.74–2.23) | 1.30 (0.68–2.49) |
| Don't remember | 36 (23.2) | 48 (15.8) | 9 (8.7) | 5 (2.6) | 5 (3.07) | 1 (0.18) | 15 (5.2) | 11 (1.5) | 14 (9.9) | 102 (21.8) | 79 (9.3) | 167 (7.4) | 1.40 (1.03–1.91) | 2.26 (1.48–3.46) |
| Fetal movement frequency (last two weeks) | ||||||||||||||
| Increased | 13 (8.4) | 85 (28.0) | 6 (5.8) | 17 (8.9) | 21 (12.9) | 217 (38.8) | 36 (12.5) | 254 (34.7) | 7 (4.9) | 75 (16.0) | 83 (9.8) | 648 (28.7) | 0.33 (0.26–0.43) | 0.29 (0.22–0.38) |
| Decreased | 45 (29.0) | 36 (11.8) | 9 (8.7) | 13 (6.8) | 61 (37.4) | 82 (14.6) | 84 (29.2) | 63 (8.6) | 66 (46.5) | 74 (15.8) | 265 (31.1) | 268 (11.9) | 2.74 (2.22–3.37) | 2.49 (1.96–3.16) |
| No change or unsure | 97 (62.6) | 183 (60.2) | 88 (85.4) | 162 (84.4) | 81 (49.7) | 261 (46.6) | 168 (58.3) | 416 (56.8) | 63 (44.4) | 225 (48.1) | 497 (58.4) | 1247 (55.3) | 1 | 1 |
Data are number (percentage) or median (IQR). TASS = The Auckland Stillbirth Study. SSS = Sydney Stillbirth Study. MCSS = New Zealand Multicentre Stillbirth Study. MiNESS = Midlands and North of England Stillbirth Study. STARS = Study of Trends and Associated Risks for Stillbirth Study. CRIBSS = Collaborative IPD of Sleep and Stillbirth. Multivariable models are adjusted for matching terms (gestation at interview in controls and at diagnosis of stillbirth for cases) and study and site, and all the other variables in the table. Participants with missing data were excluded from the multivariable model. No imputation for missing data. *South Asian includes India, Pakistan, Sri Lanka, Bangladesh, Nepal, Bhutan, the Maldives, and Afghanistan ethnicities.