Table 3 Association between maternal blood metal concentrations during first trimester with spontaneous preterm birth risk

15 (12.5)/46 (38.3)

26 (21.7)/34 (28.3)

2.30 (1.01,5.26)

0.047

2.22 (0.91,5.41)

0.080

35 (29.2)/26 (21.7)

2.99 (1.34,6.65)

0.007

3.36 (1.39,8.13)

0.007

44 (36.7)/14 (11.7)

5.91 (2.63,13.31)

 < 0.001

5.76 (2.46,13.53)

 < 0.001

 < 0.001

 < 0.001

31 (25.8)/31 (25.8)

35 (29.2)/32 (26.7)

1.10 (0.55,2.20)

0.791

1.01 (0.48,2.14)

0.975

29 (24.2)/31 (25.8)

0.94 (0.47,1.87)

0.860

0.99 (0.44,2.23)

0.973

25 (20.8)/26 (21.7)

0.98 (0.46,2.06)

0.948

1.03 (0.50,2.16)

0.930

0.818

0.996

33 (27.5)/27 (22.5)

27 (22.5)/34 (28.3)

0.63 (0.30,1.32)

0.220

0.61 (0.27,1.38)

0.233

29 (24.2)/30 (25.0)

0.83 (0.41,1.68)

0.598

0.79 (0.37,1.68)

0.537

31 (25.8)/29 (24.2)

0.91 (0.46,1.78)

0.777

0.89 (0.42,1.90)

0.771

0.867

0.854

27 (22.5)/34 (28.3)

37 (30.8)/22 (18.3)

1.92 (0.95,3.87)

0.069

1.55 (0.72,3.34)

0.260

25 (20.8)/36 (30.0)

0.81 (0.39,1.68)

0.566

0.99 (0.45,2.16)

0.980

31 (25.8)/28 (23.3)

1.26 (0.64,2.46)

0.499

1.33 (0.64,2.75)

0.445

0.913

0.627

28 (23.3)/45 (37.5)

25 (20.8)/29 (24.2)

1.38 (0.68,2.77)

0.37

1.45 (0.68,3.09)

0.333

28 (23.3)/28 (23.3)

1.50 (0.77,2.94)

0.237

1.54 (0.74,3.20)

0.243

39 (32.5)/18 (15.0)

3.27 (1.56,6.85)

0.002

3.64 (1.64,8.09)

0.002

0.002

0.003

38 (31.7)/22 (18.3)

30 (25.0)/30 (25.0)

0.57 (0.27,1.21)

0.141

0.42 (0.18,0.96)

0.041

23 (19.2)/37 (30.8)

0.34 (0.16,0.75)

0.008

0.32 (0.13,0.76)

0.010

29 (24.2)/31 (25.8)

0.58 (0.29,1.18)

0.133

0.53 (0.24,1.16)

0.111

0.066

0.095

33 (27.5)/29 (24.2)

31 (25.8)/29 (24.2)

0.91 (0.44,1.88)

0.796

0.97 (0.43,2.19)

0.947

27 (22.5)/33 (27.5)

0.70 (0.33,1.48)

0.353

0.60 (0.26,1.35)

0.216

29 (24.2)/29 (24.2)

0.86 (0.39,1.89)

0.709

0.89 (0.36,2.21)

0.803

0.536

0.405

42 (35.0)/44 (36.7)

20 (16.7)/32 (26.7)

0.66 (0.33,1.33)

0.241

0.46 (0.21,1.02)

0.057

28 (23.3)/21 (17.5)

1.41 (0.65,3.02)

0.382

1.57 (0.69,3.59)

0.286

30 (25.0)/23 (19.2)

1.37 (0.71,2.66)

0.346

1.27 (0.61,2.64)

0.519

0.224

0.270

31 (25.8)/29 (24.2)

24 (20.0)/36 (30.0)

0.64 (0.31,1.31)

0.221

0.48 (0.22,1.05)

0.067

31 (25.8)/29 (24.2)

0.97 (0.47,2.00)

0.925

0.98 (0.43,2.21)

0.960

34 (28.3)/26 (21.7)

1.26 (0.59,2.68)

0.549

1.15 (0.50,2.64)

0.735

0.349

0.377

36 (30.0)/24 (20.0)

27 (22.5)/33 (27.5)

0.50 (0.23,1.08)

0.079

0.54 (0.24,1.22)

0.140

35 (29.2)/26 (21.7)

0.96 (0.44,2.07)

0.908

0.99 (0.42,2.32)

0.983

22 (18.3)/37 (30.8)

0.39 (0.18,0.84)

0.015

0.39 (0.17,0.91)

0.029

0.063

0.078

28 (23.3)/38 (31.7)

26 (21.7)/30 (25.0)

1.15 (0.57,2.32)

0.692

1.05 (0.49,2.25)

0.907

35 (29.2)/23 (19.2)

2.01 (0.99,4.10)

0.054

1.56 (0.75,3.28)

0.236

31 (25.8)/29 (24.2)

1.47 (0.70,3.09)

0.304

1.70 (0.78,3.72)

0.182

0.131

0.116

23 (19.2)/37 (30.8)

29 (24.2)/31 (25.8)

1.35 (0.64,2.86)

0.428

1.06 (0.48,2.38)

0.880

30 (25.0)/30 (25.0)

1.41 (0.67,2.94)

0.366

1.35 (0.60,3.01)

0.465

38 (31.7)/22 (18.3)

2.53 (1.23,5.20)

0.012

2.88 (1.29,6.41)

0.010

0.015

0.010

28 (23.3)/32 (26.7)

26 (21.7)/34 (28.3)

0.88 (0.44,1.76)

0.723

0.91 (0.44,1.89)

0.801

33 (27.5)/27 (22.5)

1.54 (0.71,3.31)

0.273

1.64 (0.73,3.69)

0.233

33 (27.5)/27 (22.5)

1.48 (0.70,3.12)

0.308

1.49 (0.67,3.32)

0.329

0.187

0.208

28 (23.3)/32 (26.7)

29 (24.2)/31 (25.8)

1.09 (0.54,2.21)

0.814

1.12 (0.52,2.41)

0.780

26 (21.7)/34 (28.3)

0.90 (0.43,1.90)

0.787

0.86 (0.38,1.92)

0.705

37 (30.8)/23 (19.2)

1.98 (0.91,4.33)

0.086

2.30 (1.00,5.28)

0.049

0.146

0.091