Table 1 General characteristics of study participants
From: Associations of COVID-19 lockdown with gestational length and preterm birth in China
|  | Unexposed group (n = 493,496) No. of participants (%) | Exposed group (n = 101,900) No. of participants0 (%) | χ2 | P |
Maternal age (years) | ||||
 < 24 | 50,255 (10.2) | 8412 (8.3) | 660.24 | < 0.001 |
 24–26 | 81,222 (16.5) | 15,864 (15.6) | ||
 27–29 | 118,040 (23.9) | 23,723 (23.3) | ||
 30–32 | 102,817 (20.8) | 23,585 (23.1) | ||
 33–35 | 72,330 (14.7) | 16,094 (15.8) | ||
 > 35 | 68,832 (13.9) | 14,222 (13.9) | ||
Residential city | ||||
 Guangzhou | 19,850 (4.0) | 2970 (2.9) | 1193.80 | < 0.001 |
 Dongguan | 34,579 (7.0) | 5641 (5.5) | ||
 Jiangmen | 18,107 (3.7) | 3303 (3.3) | ||
 Shenzhen | 75,334 (15.3) | 13,280 (13.0) | ||
 Foshan | 345,626 (70.0) | 76,706 (75.3) | ||
Infant sex | < 0.01 | 0.950 | ||
 Male | 263,153 (53.3) | 54,349 (53.3) | ||
 Female | 230,343 (46.7) | 47,551 (46.7) | ||
Pregnancy complications (N = 173,064)a | ||||
 Hypertensive disorders of pregnancy (HDP) | ||||
  No | 143,933 (97.3) | 24,369 (96.7) | 96.57 | < 0.001 |
  Yes | 3937 (2.7) | 825 (2.3) | ||
   Gestational hypertension | 971 (0.7) | 252 (1.0) | ||
   Pre-eclampsia / Eclampsia | 2712 (1.8) | 473 (1.9) | ||
   Chronic hypertension | 141 (0.1) | 44 (0.2) | ||
   Chronic hypertension with superimposed pre-eclampsia | 113 (0.1) | 56 (0.2) | ||
 Gestational diabetes mellitus (GDM) | ||||
  No | 129,653 (87.7) | 21,313 (84.6) | 183.64 | < 0.001 |
  Yes | 18,217 (12.3) | 3881 (15.4) | ||
Preterm birth | ||||
 No | 467,865 (94.8) | 96,307 (94.5) | 15.58 | < 0.001 |
 Yes | 25,631 (5.2) | 5593 (5.5) | ||
  Very premature (< 32 GWs) | 2121 (0.4) | 443 (0.4) | ||
  Moderate/late premature (32–36 GWs) | 23,510 (4.8) | 5150 (5.1) | ||
Stillbirth (N = 595,904) | ||||
 No | 493,496 (99.92) | 101,900 (99.90) | 3.36 | 0.067 |
 Yes | 405 (0.08) | 103 (0.10) | ||
Marital status | ||||
 Married | 488,376 (99.0) | 100,631 (98.8) | 472.03 | < 0.001 |
 Unmarried | 4263 (0.8) | 732 (0.7) | ||
 Other | 857 (0.2) | 537 (0.5) | ||
Parity | ||||
 0 (Primiparas) | 415,074 (84.1) | 79,686 (78.2) | 2121.60 | < 0.001 |
 1 (Multiparas) | 63,158 (12.8) | 17,603 (17.3) | ||
 2–4 (Multiparas) | 15,264 (3.1) | 4611 (4.5) | ||
Delivery type | ||||
 Natural delivery | 297,591 (60.3) | 63,394 (62.2) | 1871.40 | < 0.001 |
 Operative vaginal delivery | 16,735 (3.4) | 1055 (1.0) | ||
 Cesarean delivery | 179,027 (36.3) | 37,298 (36.6) | ||
 Other | 143 (< 0.1) | 153 (0.2) | ||
|  | Mean ± SD | Mean ± SD | t | P |
Maternal age (years) | 29.78 ± 5.09 | 30.07 ± 4.94 | 17.11 | < 0.001 |
Gestational length (week Mean ± SD) | 38.74 ± 1.46 | 38.66 ± 1.46 | 16.22 | < 0.001 |