Table 1 Maternal and Perinatal Baseline Characteristics
|  | PE group (N = 2988) | non-PE group (N = 113,054) | χ2 | P |
|---|---|---|---|---|
Gravidity | Â | Â | 1.437 | 0.231 |
 1 | 1089 (36.4) | 40,002 (35.4) |  |  |
  ≥ 2 | 1899 (63.6) | 73,052 (64.6) | ||
Parity | 40.137 | < 0.001 | ||
 0 | 1413 (47.3) | 49,479 (43.8) |  |  |
 1 | 1355 (45.3) | 57,234 (50.6) | ||
  ≥ 2 | 220 (7.4) | 6341 (5.6) | ||
Age (years) | 176.188 | < 0.001 | ||
  < 20 | 47 (1.6) | 1304 (1.2) |  |  |
 20–24 | 472 (15.8) | 18,094 (16.0) | ||
 25–29 | 1201 (40.2) | 53,034 (46.9) | ||
 30–34 | 753 (25.2) | 28,463 (25.2) | ||
 35–39 | 406 (13.6) | 10,451 (9.2) | ||
  ≥ 40 | 109 (3.6) | 1708 (1.5) | ||
Education level | 84.782 | < 0.001 | ||
 College and above | 956 (32.0) | 41,755 (36.9) |  |  |
 Middle school | 1921 (64.3) | 69,307 (61.3) | ||
 Primary school and below | 111 (3.7) | 1992 (1.8) | ||
Marital status | 0.272 | 0.602 | ||
 Married | 2974 (99.5) | 112,594 (99.6) |  |  |
 Single or divorced | 14 (0.5) | 460 (0.4) | ||
Season of conception | 0.134 | 0.714 | ||
 Warm (May to October) | 1396 (46.7) | 53,202 (47.1) |  |  |
 Cold (November to April) | 1592 (53.3) | 59,852 (52.9) | ||
Season of delivery | 3.668 | 0.160 | ||
 Warm (May to October) | 1304 (43.6) | 48,700 (43.1) |  |  |
 Cold (November to April) | 1361 (45.5) | 53,111 (47.0) | ||
Gestational age (weeks) |  |  | 5201.901 | < 0.001 |
  ≥ 37 | 1834 (61.4) | 106,660 (94.3) |  |  |
  < 37 | 1154 (38.6) | 6394 (5.7) |  |  |