Table 3.
Association between maternal sociodemographic and obstetric characteristics and preterm birth according to gestational age in all pregnancies in China, 2012–18
|
Model 1 (adjusted odds ratio)*† |
Model 2 (adjusted odds ratio)*†‡ | |||||||
|---|---|---|---|---|---|---|---|---|
| All preterm | Very preterm | Moderate preterm | Late preterm | All preterm | Very preterm | Moderate preterm | Late preterm | |
| Region | ||||||||
| East | 1·28 (1·07-1·53) | 1·34 (0·93–1·93) | 1·31 (0·96–1·81) | 1·26 (1·10–1·45) | 1·23 (1·02–1·47) | 1·27 (0·88–1·83) | 1·25 (0·91–1·72) | 1·22 (1·06–1·40) |
| Central | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) |
| West | 1·15 (0·99–1·33) | 1·07 (0·82–1·40) | 1·14 (0·90–1·44) | 1·16 (1·02–1·31) | 1·11 (0·96–1·29) | 1·03 (0·78–1·34) | 1·09 (0·86–1·39) | 1·13 (1·00–1·28) |
| Maternal education | ||||||||
| Illiterate | 1·50 (1·27–1·79) | 1·88 (1·49–2·37) | 2·03 (1·64–2·52) | 1·37 (1·17–1·61) | 1·43 (1·22–1·68) | 1·78 (1·43–2·21) | 1·92 (1·57–2·35) | 1·31 (1·13–1·52) |
| Primary school | 1·21 (1·13–1·30) | 1·44 (1·28–1·62) | 1·40 (1·26–1·56) | 1·15 (1·08–1·23) | 1·15 (1·08–1·23) | 1·37 (1·23–1·52) | 1·32 (1·20–1·46) | 1·10 (1·04–1·17) |
| Middle school | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) |
| High school | 1·35 (1·25–1·46) | 1·67 (1·45–1·91) | 1·57 (1·39–1·78) | 1·29 (1·21–1·37) | 1·36 (1·26–1·46) | 1·69 (1·48–1·93) | 1·59 (1·41–1·78) | 1·29 (1·21–1·37) |
| College or higher | 1·56 (1·43–1·71) | 2·19 (1·85–2·61) | 1·93 (1·68–2·23) | 1·45 (1·35–1·56) | 1·53 (1·40–1·68) | 2·16 (1·82–2·56) | 1·90 (1·65–2·18) | 1·42 (1·32–1·53) |
| Marital status | ||||||||
| Married | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) |
| Single, widowed, or divorced | 1·30 (1·14–1·49) | 1·49 (1·18–1·88) | 1·38 (1·16–1·64) | 1·26 (1·12–1·42) | 1·28 (1·11–1·48) | 1·46 (1·15–1·87) | 1·35 (1·13–1·63) | 1·24 (1·09–1·41) |
| Maternal age (years) | ||||||||
| <20 | 1·32 (1·25–1·40) | 1·55 (1·39–1·72) | 1·65 (1·50–1·82) | 1·25 (1·19–1·31) | 1·46 (1·38–1·54) | 1·73 (1·56–1·93) | 1·86 (1·68–2·05) | 1·37 (1·30–1·44) |
| 20–24 | 0·98 (0·95–1·00) | 0·96 (0·91–1·02) | 1·03 (0·98–1·08) | 0·97 (0·95–0·99) | 1·02 (0·99–1·05) | 1·02 (0·96–1·08) | 1·09 (1·03–1·14) | 1·01 (0·99–1·04) |
| 25–29 | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) |
| 30–34 | 1·28 (1·25–1·31) | 1·39 (1·33–1·47) | 1·33 (1·28–1·39) | 1·26 (1·24–1·29) | 1·22 (1·19–1·25) | 1·32 (1·25–1·40) | 1·26 (1·20–1·32) | 1·21 (1·18–1·23) |
| 35–39 | 1·75 (1·70–1·81) | 2·05 (1·92–2·20) | 1·88 (1·78–1·98) | 1·70 (1·65–1·75) | 1·55 (1·49–1·61) | 1·79 (1·66–1·92) | 1·63 (1·53–1·74) | 1·51 (1·46–1·55) |
| 40–44 | 2·24 (2·14–2·34) | 2·53 (2·31–2·77) | 2·47 (2·29–2·66) | 2·17 (2·09–2·25) | 1·84 (1·76–1·93) | 2·03 (1·84–2·23) | 1·97 (1·81–2·14) | 1·80 (1·73–1·88) |
| 45–49 | 2·31 (2·11–2·52) | 2·37 (1·96–2·88) | 2·41 (2·04–2·84) | 2·29 (2·07–2·52) | 1·87 (1·71–2·06) | 1·87 (1·55–2·26) | 1·89 (1·59–2·25) | 1·87 (1·69–2·08) |
| Antenatal visits | ||||||||
| None | 1·80 (1·48–2·19) | 2·72 (2·07–3·55) | 2·44 (1·92–3·10) | 1·55 (1·31–1·85) | 1·78 (1·47–2·16) | 2·71 (2·08–3·52) | 2·43 (1·91–3·07) | 1·54 (1·30–1·83) |
| 1–3 | 1·44 (1·30–1·59) | 2·04 (1·77–2·35) | 1·71 (1·49–1·96) | 1·31 (1·20–1·43) | 1·40 (1·27–1·54) | 1·99 (1·73–2·28) | 1·66 (1·46–1·90) | 1·27 (1·17–1·39) |
| 4–6 | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) |
| 7–9 | 0·80 (0·73–0·87) | 0·52 (0·45–0·60) | 0·64 (0·56–0·72) | 0·87 (0·80–0·95) | 0·76 (0·69–0·83) | 0·49 (0·42–0·57) | 0·60 (0·53–0·67) | 0·83 (0·76–0·90) |
| ≥10 | 0·50 (0·43–0·59) | 0·33 (0·24–0·46) | 0·39 (0·30–0·51) | 0·55 (0·48–0·63) | 0·47 (0·40–0·54) | 0·31 (0·23–0·42) | 0·36 (0·28–0·47) | 0·51 (0·45–0·58) |
| Parity | ||||||||
| Primiparous | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) |
| Multiparous | 0·96 (0·91–1·00) | 0·97 (0·88–1·07) | 0·97 (0·89–1·06) | 0·95 (0·92–0·99) | 1·07 (1·01–1·13) | 1·10 (0·99–1·23) | 1·10 (0·99–1·22) | 1·05 (1·01–1·10) |
| Type of pregnancy | ||||||||
| Singleton | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) |
| Multiple | 17·56 (16·54–18·64) | 17·82 (16·79–18·91) | 20·56 (19·24–21·97) | 17·07 (16·03–18·17) | 15·51 (14·44–16·67) | 15·48 (14·46–16·58) | 17·81 (16·54–19·18) | 15·17 (14·08–16·34) |
| Maternal complications | ||||||||
| Antepartum complications | .. | .. | .. | .. | 3·91 (3·66–4·17) | 4·80 (4·26–5·41) | 4·88 (4·32–5·51) | 3·67 (3·47–3·87) |
| Medical disease | .. | .. | .. | .. | 1·57 (1·47–1·68) | 1·47 (1·31–1·65) | 1·63 (1·44–1·84) | 1·58 (1·49–1·67) |
| None of the above | .. | .. | .. | .. | 1 (ref) | 1 (ref) | 1 (ref) | 1 (ref) |
Data are odds ratio (95% CI). 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 sampling distribution of the population.
†
Adjusted for the clustering of births within hospitals and maternal sociodemographic characteristics (region, maternal education, maternal age, marital status, antenatal visits, parity, and type of pregnancy).
‡
Adjusted for maternal complications.