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Table 2 Descriptive statistics of SGA and mean exposure over the entire pregnancy among characteristics of the included 2709 preterm births

From: Effect of ambient air pollution on premature SGA in Changzhou city, 2013–2016: a retrospective study

Characteristic

SGA a [n (%)]

Mean PM2.5 (μg/m3)

Mean SO2 (μg/m3)

Mean NO2 (μg/m3)

gender

 male

250 (9.4)

51.22

76.55

105.75

 female

189 (7.1)

50.98

76.12

105.55

P

0.000 *

0.849

0.725

0.354

Maternal age (years) b

 <  20

16 (0.6)

48.85

72.73

105.36

 20–30

296 (11.4)

51.05

76.33

105.82

 30–40

112 (4.3)

51.51

76.66

104.65

 >  40

7 (0.3)

50.77

75.76

108.82

P

0.000 *

0.290

0.458

0.666

Birth years

 2013

32 (1.2)

49.75

70.29

110.77

 2014

130 (4.0)

49.70

73.64

113.37

 2015

136 (4.8)

50.05

75.43

100.40

 2016

141 (5.2)

53.48

80.72

102.55

P

0.747

0.079

0.279

0.571

Season of birth

 Spring

96 (3.5)

52.06

77.91

103.21

 Summer

105 (3.9)

46.87

67.37

101.65

 Fall

126 (4.7)

51.85

77.68

107.75

 Winter

112 (4.1)

53.19

81.47

109.05

P

0.562

0.001*

0.000 *

0.000 *

Natural delivery

 No

110 (4.1)

49.43

74.13

104.31

 Yes

329 (12.1)

52.42

78.10

106.71

P

0.000 *

0.549

0.000 *

0.127

Parity

 Once

151 (5.6)

50.68

75.43

106.23

 Twice or more

288 (10.6)

51.68

77.37

105.97

P

0.000 *

0.368

0.715

0.729

  1. a SGA: small for gestational age
  2. b missing 58 subjects
  3. * P < 0.05