Table 1 Characteristics of cases and controls from Changsha included in the study, 2015–2018
Characteristics | Controls (n = 4460) | Overall Cases (n = 446) | P valuea | Cleft palate only (n = 75) | |||
|---|---|---|---|---|---|---|---|
N | (%) | N | (%) | N | (%) | ||
Maternal age (years) | < 0.0001 | ||||||
< 20 | 14 | 0.31 | 5 | 1.12 | 0 | 0.00 | |
20–24 | 363 | 8.14 | 68 | 15.25 | 12 | 16.00 | |
25–29 | 1982 | 44.44 | 189 | 42.38 | 33 | 44.00 | |
≥ 30 | 2101 | 47.11 | 184 | 41.26 | 30 | 40.00 | |
Maternal education | < 0.0001 | ||||||
Middle school or below | 0 | 0.00 | 60 | 13.45 | 10 | 13.33 | |
High/technical school | 1392 | 31.21 | 128 | 28.70 | 18 | 24.00 | |
College or higher degree | 3068 | 68.79 | 258 | 57.85 | 47 | 62.67 | |
Gravidity | < 0.0001 | ||||||
1 | 1559 | 34.96 | 106 | 23.77 | 21 | 28.00 | |
2 | 1315 | 29.48 | 131 | 29.37 | 24 | 32.00 | |
3 | 799 | 17.91 | 101 | 22.65 | 12 | 16.00 | |
≥ 4 | 787 | 17.65 | 108 | 24.22 | 18 | 24.00 | |
Season of conception | 0.0742 | ||||||
Warm | 2615 | 58.63 | 242 | 54.26 | 44 | 58.67 | |
Cold | 1845 | 41.37 | 204 | 45.74 | 31 | 41.33 | |
Plurality | 0.1397 | ||||||
Singleton | 4252 | 93.95 | 432 | 96.86 | 74 | 98.67 | |
Multiple birth | 208 | 6.05 | 14 | 3.14 | 1 | 1.33 | |
Infant sexb | 0.0004 | ||||||
Female | 2135 | 47.62 | 174 | 39.01 | 36 | 48.00 | |
Male | 2325 | 52.38 | 272 | 60.99 | 39 | 52.00 | |