Table 2

Rates of PTB, LBW and SGA according to demographic characteristics, residence address and birth season by year

YearCharacteristicAdverse pregnancy outcome
PTB (%)P valueLBW (%)P valueSGA (%)P value
2014Maternal age (years)<0.0001<0.0001<0.0001
 <353.794.0414.39
 ≥356.435.1710.54
Inhabited city<0.0001<0.0001<0.0001
 Pearl River Delta region5.034.4911.75
 Non-Pearl River Delta region3.393.9115.43
Infant sex<0.0001<0.0001<0.0001
 Boy4.433.6313.81
 Girl3.474.6814.46
Season of birth<0.00010.0003<0.0001
 Spring3.783.9613.85
 Summer3.854.1914.88
 Autumn3.84.2114.88
 Winter4.484.112.8
2015Maternal age (years)<0.0001<0.0001<0.0001
 <353.794.0514.09
 ≥356.54.919.51
Inhabited city<0.0001<0.0001<0.0001
 Pearl River Delta region5.134.4811.06
 Non-Pearl River Delta region3.433.9315.12
Infant sex<0.0001<0.0001<0.0001
 Boy4.513.6813.43
 Girl3.474.6314.01
Season of birth<0.0001<0.0001<0.0001
 Spring4.024.0813.36
 Summer4.034.3314.59
 Autumn3.874.1914.24
 Winter4.23.8712.53
2016Maternal age (years)<0.0001<0.0001<0.0001
 <354.243.9812.4
 ≥356.874.888.5
Inhabited city<0.0001<0.0001<0.0001
 Pearl River Delta region5.284.259.9
 Non-Pearl River Delta region3.823.9213.93
Infant sex<0.0001<0.0001<0.0001
 Boy5.023.6111.7
 Girl44.6212.23
Season of birth0.0011<0.0001<0.0001
 Spring4.494.0211.76
 Summer4.664.2912.37
 Autumn4.434.0812.01
 Winter4.63.9311.58
2017Maternal age (years)<0.0001<0.0001<0.0001
 <353.674.1113.85
 ≥355.834.8910.05
Inhabited city<0.0001<0.0001<0.0001
 Pearl River Delta region4.274.4212.56
 Non-Pearl River Delta region3.824.0813.82
Infant sex<0.0001<0.00010.1572
 Boy4.533.7813.13
 Girl3.54.7813.24
Season of birth<0.0001<0.0001<0.0001
 Spring3.914.1412.57
 Summer3.944.3613.91
 Autumn3.984.4614.23
 Winter4.364.0412.02
  • LBW, low birth weight; PTB, preterm birth; SGA, small for gestational age.