Table 1

Basic characteristics of the study participants

CharacteristicCategoryFrequencyPercentage
Maternal age (years)<2078 1162.68
20–24664 44322.78
25–291 163 07139.87
30–34682 06723.38
≥35329 37811.29
Missing230.00
Inhabited cityPearl River Delta region1 254 10242.99
Non-Pearl River Delta region1 662 99657.01
Infant sexBoy1 553 94853.27
Girl1 363 12546.73
Missing250.00
Year of birth2014763 51826.17
2015627 14621.50
2016794 75527.24
2017731 67925.08
Season of birthSpring675 59523.16
Summer717 76224.61
Autumn804 27527.57
Winter719 46624.66
Preterm birthYes121 2454.16
No2 792 95395.74
Missing29000.10
LBWYes120 8464.14
No2 796 12295.85
Missing1300.00
SGAYes384 63712.86
No2 529 52282.88
Missing29394.26
LBW (Yes)Preterm56 74846.96
Full-term63 96852.93
Missing1300.11
SGA (Yes)Preterm94992.47
Full-term375 13897.53
  • LBW, low birth weight; SGA, small for gestational age.