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Table 1 Characteristics and five air pollutant concentrations of normotensive, gestational hypertension, preeclampsia and Mg-preeclampsia groups in 18,835 pregnant women residing in Seoul for 2002–2013 from the Korean National Health Insurance Service–National Sample Cohort

From: Exposure to air pollution during preconceptional and prenatal periods and risk of hypertensive disorders of pregnancy: a retrospective cohort study in Seoul, Korea

Characteristics

Normotensive group N = 18,565

Gestational hypertension N = 105

Preeclampsia N = 88

Mg-preeclampsia N = 77

Maternal age (years)

 15–24

542 (2.9)

3 (2.8)

4 (4.5)

0 (0)

 25–34

14,564 (78.4)

70 (66.7)a

65 (73.9)

57 (74.0)

 35–44

3459 (18.7)

32 (30.5)a

19 (21.6)

20 (26.0)

Paid employment

5309 (28.6)

32 (30.5)

23 (26.1)

22 (28.6)

Nulliparity

10,551 (56.8)

69 (65.7)

67 (76.1)a

53 (68.8)a

Multiple gestation

268 (1.4)

2 (1.9)

7 (8.0)a

7 (9.1)a, b

Diagnosis of diabetes

297 (1.6)

8 (7.6)a

7 (8.0)a

7 (9.1)a

Household income (%)

 0–40

3509 (18.9)

27 (25.7)a

14 (15.9)

16 (20.8)

 40–70

7607 (41.0)

51 (48.6)a

42 (47.7)

38 (49.3)

 70–100

7449 (40.1)

27 (25.7)a

32 (36.4)

23 (29.9)

Birth season

 Spring

4689 (25.3)

34 (32.4)

22 (25.0)

22 (28.6)

 Summer

4288 (23.1)

22 (21.0)

17 (19.3)

23 (29.9)

 Fall

4916 (26.5)

27 (25.7)

30 (34.1)

18 (23.3)

 Winter

4672 (25.1)

22 (21.0)

19 (21.6)

14 (18.2)

PM10 (μg/m3) for four exposure periods

 12 months to birth

57.78 ± 10.31

54.72 ± 10.40a

58.08 ± 11.57

58.15 ± 9.81b

 6 months

56.23 ± 13.56

54.11 ± 13.75

54.64 ± 14.11

55.84 ± 13.22

 3 months

56.34 ± 16.68

54.15 ± 15.58

52.72 ± 14.80a

56.56 ± 16.99

 1 month

56.68 ± 20.40

53.12 ± 16.58

52.95 ± 17.79 a

53.40 ± 17.64

NO2 (ppb)

 12 months

35.33 ± 4.42

34.10 ± 4.51a

35.07 ± 4.97

36.31 ± 4.38b

 6 months

35.12 ± 5.85

33.99 ± 5.38a

34.51 ± 6.27

36.02 ± 5.84b

 3 months

35.19 ± 7.22

34.30 ± 6.50

34.41 ± 7.09

35.43 ± 7.82

 1 month

35.33 ± 8.47

33.70 ± 7.07a

35.13 ± 7.54

34.62 ± 9.52

CO (100 ppb)

 12 months

76.16 ± 14.45

73.13 ± 13.80a

77.34 ± 16.43

77.65 ± 12.13b

 6 months

75.20 ± 18.93

72.23 ± 17.41

75.42 ± 19.83

77.27 ± 19.58

 3 months

75.28 ± 23.28

72.72 ± 19.94

74.41 ± 22.76

76.03 ± 23.92

 1 month

75.24 ± 25.85

70.69 ± 21.54

73.12 ± 23.17

74.24 ± 29.24

SO2 (ppb)

 12 months

5.25 ± 1.06

5.12 ± 0.90

5.35 ± 1.10

5.18 ± 1.09

 6 months

5.24 ± 1.43

5.11 ± 1.24

5.20 ± 1.47

5.31 ± 1.57

 3 months

5.27 ± 1.74

5.26 ± 1.53

5.21 ± 1.81

5.17 ± 1.77

 1 month

5.29 ± 1.99

5.17 ± 1.56

5.35 ± 1.96

4.97 ± 2.15

O3 (ppm)

 12 months

29.74 ± 4.93

31.33 ± 4.28

29.51 ± 5.11b

29.49 ± 5.21b

 6 months

29.54 ± 8.90

29.87 ± 8.39

29.56 ± 9.67

28.55 ± 9.12

 3 months

29.36 ± 11.40

29.62 ± 10.46

28.20 ± 10.76

30.67 ± 11.98

 1 month

29.54 ± 12.86

30.37 ± 11.92

27.71 ± 11.04

31.70 ± 13.94

  1. PM10 particulate matter, NO2 nitrogen dioxide, CO carbon monoxide, SO2 sulfur dioxide, O3 ozone
  2. Numbers presented in parentheses are percentages. Concentrations of air pollutants are shown as mean ± standard deviation. Pearson’s Chi-squared test with Yates’ continuity correction was used for comparison between pairs of normotensive and three hypertensive disorder groups. Student t test was used for comparison of period-average concentrations of the five air pollutants between pairs of normotensive and three hypertensive disorder groups
  3. aSignificant difference (p < .05) compared with the normotensive group. bSignificant difference (p < .05) compared with the gestational hypertension group. No significant differences between preeclampsia and Mg-preeclampsia groups