Table 1.
Characteristics in relation to gestational age
| Normal term ≥ 37 weeks (n = 1804) |
Very preterm < 32 weeks (n = 363) |
Moderate preterm 32–33 weeks (n = 306) |
Late preterm 34–36 weeks (n = 730) |
Total preterm < 37 weeks (n = 1399) |
P* | |
|---|---|---|---|---|---|---|
| Socioeconomic status (SES) | ||||||
| Individual components of SES | ||||||
| Maternal education level(%) | ||||||
| Postgraduate | 201(11.1) | 14(3.8) | 8(2.6) | 34(4.7) | 56(4.0) | < 0.001 |
| College graduate | 1234(68.4) | 142(39.1) | 137(44.8) | 373(51.1) | 652(46.6) | |
| Senior school | 225(12.5) | 108(29.8) | 86(28.1) | 167(22.9) | 361(25.8) | |
| Junior school and below | 144(8.0) | 99(27.3) | 75(24.5) | 156(21.3) | 330(23.6) | |
| Paternal education level (%) | ||||||
| Postgraduate | 212(11.8) | 17(4.7) | 10(3.3) | 45(6.2) | 72(5.1) | < 0.001 |
| College graduate | 1217(67.5) | 149(41.1) | 139(45.4) | 372(50.9) | 660(47.2) | |
| Senior school | 257(14.2) | 110(30.3) | 87(28.4) | 165(22.6) | 362(25.9) | |
| Junior school and below | 118(6.5) | 87(23.9) | 70(22.9) | 148(20.3) | 305(21.8) | |
| Family income (◊thousands, Yuan) (%) | ||||||
| < 50 | 247(13.7) | 121(33.3) | 99(32.4) | 209(28.6) | 429(30.7) | < 0.001 |
| 50- | 1013(56.2) | 184(50.7) | 141(46.1) | 356(48.8) | 681(48.7) | |
| 100- | 501(27.8) | 57(15.7) | 61(19.9) | 154(21.1) | 272(19.4) | |
| 300- | 43(2.4) | 1(0.3) | 5(1.6) | 11(1.5) | 17(1.2) | |
| Composite SES | ||||||
SES ( ) |
9.85 ± 1.67 | 8.22 ± 2.16 | 8.38 ± 2.17 | 8.73 ± 2.19 | 8.52 ± 2.19 | < 0.001 |
Weighted-SES ( ) |
10.22 ± 1.72 | 8.52 ± 2.25 | 8.68 ± 2.24 | 9.06 ± 2.25 | 8.84 ± 2.26 | < 0.001 |
| SES group (%) | < 0.001 | |||||
| Low SES | 1198(66.4) | 314(86.5) | 260(85.0) | 579(79.3) | 1153(82.4) | |
| High SES | 606(33.6) | 49(13.5) | 46(15.0) | 151(20.7) | 246(17.6) | |
| Gestational weight gain (GWG) | ||||||
Mean GWG (Kg,  ) |
15.72 ± 4.88 | 11.20 ± 4.96 | 12.81 ± 4.53 | 13.99 ± 4.68 | 13.00 ± 4.87 | < 0.001 |
| GWG group | < 0.001 | |||||
| Inadequate GWG | 283(15.7) | 197(54.3) | 119(38.9) | 200(27.4) | 516(36.9) | |
| Adequate GWG | 1521(84.3) | 166(45.7) | 187(61.9) | 530(72.6) | 883(63.1) | |
| Characteristics from newborn and its parents | ||||||
| Sex of newborn (%) | 0.001 | |||||
| Male | 890(49.3) | 211(58.1) | 180(58.8) | 383(52.5) | 774(55.3) | |
| Female | 914(50.7) | 115(41.9) | 126(41.2) | 347(47.5) | 625(44.7) | |
| Ascertainment of gestational age (%) | < 0.001 | |||||
| LMP | 1517(84.1) | 206(56.8) | 149(48.7) | 450(61.6) | 805(57.5) | |
| LMP plus B-ultrasound | 287(15.9) | 157(43.2) | 157(51.3) | 280(38.4) | 593(42.5) | |
| Delivery mode (%) | < 0.001 | |||||
| Vaginal | 1657(91.9) | 175(48.2) | 111(36.3) | 305(41.8) | 591(42.2) | |
| Cesarean | 147(8.1) | 188(51.8) | 195(63.7) | 425(58.2) | 880(57.8) | |
| Gravidity (%) | < 0.001 | |||||
| 1 | 1021(56.6) | 121(33.3) | 109(35.6) | 316(43.3) | 546(39.0) | |
| 2 | 466(25.8) | 103(28.4) | 92(30.1) | 203(27.8) | 398(28.4) | |
| 3 | 200(11.1) | 77(21.2) | 61(19.9) | 106(14.5) | 244(17.5) | |
| ≥ 4 | 117(6.5) | 62(17.1) | 44(14.4) | 105(14.4) | 211(15.1) | |
| Parity (%) | < 0.001 | |||||
| 0–1 | 1376(76.2) | 201(55.4) | 175(57.2) | 471(64.5) | 847(60.6) | |
| ≥ 2 | 428(24.8) | 162(44.6) | 131(42.8) | 259(35.5) | 552(39.4) | |
| Complications (%)** | < 0.001 | |||||
| No | 1755(97.3) | 114(31.4) | 67(21.9) | 212(29.0) | 393(28.1) | |
| Yes | 49(2.7) | 249(68.6) | 239(78.1) | 518(71.0) | 1006(71.9) | |
| Pre-pregnancy BMI (kg/m2)(%) | < 0.001 | |||||
| < 18.5 | 363(20.1) | 54(14.9) | 34(11.1) | 119(16.3) | 207(14.8) | |
| 18.5–24.9 | 1312(72.7) | 263(72.5) | 235(73.4) | 536(73.4) | 1034(73.9) | |
| 25-29.9 | 114(6.3) | 39(10.7) | 35()11.4 | 60(8.2) | 134(9.6) | |
| ≥ 30 | 15(0.8) | 7(1.9) | 2(0.65) | 15(2.1) | 24(1.7) | |
| Maternal age (years) (%) | < 0.001 | |||||
| < 25 | 168(9.3) | 59(16.3) | 45(14.7) | 87(11.9) | 191(13.7) | |
| 25- | 1008(55.9) | 136(37.4) | 131(42.8) | 349(47.8) | 616(44.0) | |
| 30- | 495(27.4) | 109(30.0) | 92(30.1) | 199(27.3) | 400(28.6) | |
| ≥ 35 | 133(7.4) | 59(16.3) | 38(12.4) | 95(13.0) | 192(13.7) | |
| Paternal age (years) (%) | < 0.001 | |||||
| < 25 | 63(3.5) | 26(7.2) | 17(5.6) | 39(5.3) | 82(5.9) | |
| 25- | 679(37.6) | 114(31.4) | 108(35.3) | 282(38.6) | 504(36.0) | |
| 30- | 745(41.3) | 121(33.3) | 106(34.6) | 250(34.3) | 477(34.1) | |
| ≥ 35 | 317(17.6) | 102(28.1) | 75(24.5) | 159(21.8) | 336(24.0) | |
Note: LMP: last menstrual period. *Comparison among normal term, very preterm, moderate term and late term newborns based on χ2 test or ANOVA. ** Refer to obstetric complications as anemia, pre-eclampsia, eclampsia, gestational hypertension, gestational diabetes, intrauterine infection, placenta previa, abruptio placentae, premature rupture of membranes, and fetal distress