Table 2.
Maternal sociodemographic and obstetric characteristics of all pregnancies according to gestational age in China, 2012–18
| Number of pregnancies (n=9 645 646) |
All preterm |
Very preterm |
Moderate preterm |
Late preterm |
|||||
|---|---|---|---|---|---|---|---|---|---|
| Rate (per 100 deliveries)* | Crude odds ratio (95% CI)*† | Rate (per 100 deliveries)* | Crude odds ratio (95% CI)*† | Rate (per 100 deliveries)* | Crude odds ratio (95% CI)*† | Rate (per 100 deliveries)* | Crude odds ratio (95% CI)*† | ||
| Region | |||||||||
| East | 2 796 175 (29·0%) | 197 604 (6·6%) | 1·19 (0·97–1·45) | 22 596 (0·7%) | 1·24 (0·84–1·82) | 27 129 (0·9%) | 1·20 (0·85–1·68) | 147 879 (5·0%) | 1·18 (1·01–1·38) |
| Central | 3 832 858 (39·7%) | 250 835 (5·7%) | 1 (ref) | 28 303 (0·6%) | 1 (ref) | 35 254 (0·7%) | 1 (ref) | 187 278 (4·3%) | 1 (ref) |
| West | 3 016 613 (31·3%) | 216 805 (6·1%) | 1·08 (0·92–1·27) | 22 782 (0·6%) | 1·01 (0·77–1·33) | 30 168 (0·8%) | 1·08 (0·84–1·38) | 163 855 (4·7%) | 1·09 (0·95–1·25) |
| Hospital level | |||||||||
| Unknown | 487 869 (5·1%) | 26 839 (4·5%) | 1·34 (0·91–1·96) | 2766 (0·4%) | 2·07 (1·19–3·60) | 3847 (0·6%) | 1·97 (1·10–3·52) | 20 226 (3·5%) | 1·22 (0·87–1·71) |
| Level 1 | 592 620 (6·1%) | 20 696 (3·4%) | 1 (ref) | 1255 (0·2%) | 1 (ref) | 1835 (0·3%) | 1 (ref) | 17 606 (2·9%) | 1 (ref) |
| Level 2 | 4 442 131 (46·1%) | 209 790 (4·5%) | 1·33 (1·15–1·53) | 16 599 (0·4%) | 1·66 (1·31–2·10) | 22 227 (0·5%) | 1·53 (1·22–1·92) | 170 964 (3·7%) | 1·28 (1·12–1·47) |
| Level 3 | 4 123 026 (42·7%) | 407 919 (9·6%) | 3·00 (2·53–3·55) | 53 061 (1·3%) | 6·27 (4·72–8·34) | 64 642 (1·5%) | 5·28 (4·05–6·87) | 290 216 (6·9%) | 2·52 (2·17–2·92) |
| Maternal education | |||||||||
| Illiterate | 46 802 (0·5%) | 5548 (10·0%) | 2·03 (1·72–2·40) | 821 (1·4%) | 2·95 (2·38–3·66) | 1034 (1·8%) | 2·94 (2·40–3·61) | 3693 (6·8%) | 1·78 (1·52–2·08) |
| Primary school | 286 364 (3·0%) | 25 939 (7·5%) | 1·50 (1·38–1·62) | 3400 (0·9%) | 1·94 (1·72–2·18) | 4199 (1·1%) | 1·83 (1·65–2·04) | 18 340 (5·5%) | 1·39 (1·29–1·50) |
| Middle school | 304 2496 (31·5%) | 181 315 (5·2%) | 1 (ref) | 18 914 (0·5%) | 1 (ref) | 24 451 (0·6%) | 1 (ref) | 137 950 (4·0%) | 1 (ref) |
| High school | 2 593 856 (26·9%) | 191 210 (6·4%) | 1·26 (1·15–1·37) | 21 539 (0·7%) | 1·39 (1·20–1·62) | 27 182 (0·9%) | 1·37 (1·19–1·56) | 142 489 (4·9%) | 1·22 (1·14–1·32) |
| College or higher | 3 473 549 (36·0%) | 241 097 (6·6%) | 1·30 (1·15–1·45) | 26 280 (0·7%) | 1·45 (1·16–1·82) | 32 364 (0·9%) | 1·38 (1·14–1·67) | 182 453 (5·0%) | 1·26 (1·15–1·39) |
| No data | 202 579 (2·1%) | 20 135 (9·4%) | .. | 2727 (1·3%) | .. | 3321 (1·5%) | .. | 14 087 (6·6%) | .. |
| Marital status | |||||||||
| Married | 9 510 128 (98·6%) | 652 621 (6·1%) | 1 (ref) | 71 926 (0·6%) | 1 (ref) | 90 500 (0·8%) | 1 (ref) | 490 195 (4·6%) | 1 (ref) |
| Single, widowed, or divorced | 133 655 (1·4%) | 12 403 (8·3%) | 1·40 (1·24–1·57) | 1727 (1·1%) | 1·77 (1·45–2·17) | 2024 (1·3%) | 1·64 (1·41–1·90) | 8652 (5·9%) | 1·30 (1·18–1·44) |
| No data | 1863 (<0·1%) | 220 (11·6%) | .. | 28 (1·5%) | .. | 27 (1·4%) | .. | 165 (8·7%) | .. |
| Maternal age (years) | |||||||||
| <20 | 238 885 (2·5%) | 19 632 (7·1%) | 1·39 (1·30–1·48) | 2564 (0·9%) | 1·74 (1·53–1·99) | 3321 (1·1%) | 1·76 (1·57–1·98) | 13 747 (5·1%) | 1·29 (1·22–1·36) |
| 20–24 | 1 852 590 (19·2%) | 109 197 (5·1%) | 0·97 (0·93–1·00) | 11 491 (0·5%) | 0·97 (0·91–1·04) | 15 617 (0·7%) | 1·02 (0·96–1·08) | 82 089 (3·9%) | 0·96 (0·93–0·98) |
| 25–29 | 3 932 312 (40·8%) | 230 965 (5·2%) | 1 (ref) | 23 887 (0·5%) | 1 (ref) | 30 709 (0·7%) | 1 (ref) | 176 369 (4·1%) | 1 (ref) |
| 30–34 | 2 275 671 (23·6%) | 169 005 (6·7%) | 1·30 (1·27–1·33) | 18 761 (0·7%) | 1·41 (1·35–1·46) | 22 969 (0·9%) | 1·35 (1·30–1·39) | 127 275 (5·1%) | 1·28 (1·26–1·30) |
| 35–39 | 872 465 (9·1%) | 84 908 (8·8%) | 1·74 (1·69–1·79) | 10 224 (1·0%) | 2·05 (1·94–2·16) | 12 004 (1·2%) | 1·88 (1·81–1·95) | 62 680 (6·6%) | 1·68 (1·64–1·72) |
| 40–44 | 188 472 (2·0%) | 22 243 (10·7%) | 2·16 (2·08–2·24) | 2694 (1·2%) | 2·51 (2·33–2·69) | 3284 (1·5%) | 2·41 (2·27–2·57) | 16 265 (8·0%) | 2·07 (2·00–2·14) |
| 45–49 | 12 165 (0·1%) | 1681 (12·1%) | 2·49 (2·22–2·79) | 196 (1·3%) | 2·74 (2·29–3·27) | 257 (1·7%) | 2·79 (2·36–3·31) | 1228 (9·1%) | 2·41 (2·12–2·74) |
| No data | 273 086 (2·8%) | 27613 (9·0%) | .. | 3864 (1·2%) | .. | 4390 (1·4%) | .. | 19 359 (6·4%) | .. |
| Antenatal visits | |||||||||
| None | 118 561 (1·2%) | 15 947 (11·3%) | 1·87 (1·45–2·40) | 2787 (1·9%) | 2·84 (2·03–3·97) | 3071 (2·1%) | 2·52 (1·86–3·42) | 10 089 (7·3%) | 1·60 (1·29–2·00) |
| 1–3 | 636 518 (6·6%) | 65 424 (8·8%) | 1·43 (1·27–1·60) | 10 814 (1·4%) | 2·00 (1·71–2·35) | 11 140 (1·4%) | 1·68 (1·45–1·95) | 43 470 (6·0%) | 1·29 (1·17–1·43) |
| 4–6 | 280 6087 (29·1%) | 211 964 (6·4%) | 1 (ref) | 26 209 (0·7%) | 1 (ref) | 31 741 (0·9%) | 1 (ref) | 154 014 (4·8%) | 1 (ref) |
| 7–9 | 2 911 415 (30·2%) | 196 907 (5·9%) | 0·93 (0·85–1·01) | 16 215 (0·5%) | 0·64 (0·55–0·74) | 23 494 (0·7%) | 0·76 (0·67–0·85) | 157 198 (4·8%) | 1·00 (0·92–1·09) |
| ≥10 | 2 898 681 (30·1%) | 138 095 (4·4%) | 0·67 (0·56–0·81) | 12 098 (0·4%) | 0·51 (0·36–0·73) | 16 306 (0·5%) | 0·56 (0·42–0·75) | 109 691 (3·5%) | 0·72 (0·61–0·83) |
| No data | 274 384 (2·8%) | 36 907 (12·5%) | .. | 5558 (1·9%) | .. | 6799 (2·2%) | .. | 24 550 (8·4%) | .. |
| Parity | |||||||||
| Primiparous | 544 0535 (56·4%) | 357 275 (5·9%) | 1 (ref) | 37 851 (0·6%) | 1 (ref) | 48 866 (0·8%) | 1 (ref) | 270 558 (4·5%) | 1 (ref) |
| Multiparous | 4 194 100 (43·5%) | 305 036 (6·3%) | 1·08 (1·03–1·12) | 35 145 (0·7%) | 1·15 (1·06–1·25) | 43 086 (0·8%) | 1·10 (1·01–1·19) | 226 805 (4·8%) | 1·06 (1·03–1·10) |
| No data | 11 011 (0·1%) | 2933 (25·3%) | .. | 685 (5·9%) | .. | 599 (5·2%) | .. | 1649 (14·2%) | .. |
| Type of pregnancy | |||||||||
| Singleton | 9 474 961 (98·2%) | 575 762 (5·4%) | 1 (ref) | 64 058 (0·6%) | 1 (ref) | 78 953 (0·7%) | 1 (ref) | 432 751 (4·1%) | 1 (ref) |
| Multiple | 170 547 (1·8%) | 89 439 (49·4%) | 17·07 (16·09–18·12) | 9606 (5·1%) | 16·79 (15·86–17·78) | 13 588 (7·2%) | 19·35 (18·18–20·59) | 66 245 (37·1%) | 16·73 (15·71–17·81) |
| No data | 138 (<0·1%) | 43 (31·5%) | .. | 17 (12·8%) | .. | 10 (7·4%) | .. | 16 (11·3%) | .. |
| Mode of delivery | |||||||||
| Vaginal | 5 292 002 (54·9%) | 292 507 (5·0%) | 1 (ref) | 38 668 (0·6%) | 1 (ref) | 40 511 (0·7%) | 1 (ref) | 213 328 (3·8%) | 1 (ref) |
| Caesarean | 435 1440 (45·1%) | 372 309 (7·4%) | 1·51 (1·40–1·63) | 34 838 (0·7%) | 1·09 (0·95–1·26) | 51 969 (1·0%) | 1·52 (1·35–1·70) | 285 502 (5·8%) | 1·58 (1·48–1·69) |
| No data | 2204 (<0·1%) | 428 (19·3%) | .. | 175 (8·1%) | .. | 71 (3·3%) | .. | 182 (8·0%) | .. |
| Maternal complications | |||||||||
| Antepartum complications | 1 899 073 (19·7%) | 309 499 (14·6%) | 4·16 (3·92–4·40) | 38 280 (1·7%) | 5·04 (4·54–5·60) | 48 394 (2·2%) | 5·18 (4·68–5·74) | 222 825 (10·8%) | 3·89 (3·71–4·09) |
| Medical disease | 694 116 (7·2%) | 46 862 (6·3%) | 1·63 (1·53–1·74) | 4108 (0·5%) | 1·44 (1·32–1·58) | 5771 (0·8%) | 1·63 (1·48–1·80) | 36 983 (5·0%) | 1·65 (1·56–1·75) |
| None of the above | 7 052 457 (73·1%) | 308 883 (4·0%) | 1 (ref) | 31 293 (0·4%) | 1 (ref) | 38 386 (0·5%) | 1 (ref) | 239 204 (3·1%) | 1 (ref) |
Data are n (%) unless otherwise stated. Very preterm babies were born after 28–31 completed weeks' gestation. Moderate preterm babies were born after 32–33 weeks' gestation. Late preterm babies were born after 34–36 weeks' gestation.
‡Adjusted for the clustering of births within hospitals.
†
Adjusted for the sampling distribution of the population.