Table 4 Association of maternal CRP, C3, C4 and ferritin levels and the risk of PTB in the second trimester

CRP

0.211

 P50 < 14.9700

48

115

1.00

–

1.00

–

 P50 - P75 (14.9700–20.8375)

35

59

1.48 (0.83–2.64)

0.179

1.50 (0.84–2.66)

0.173

 P75 > 20.8375

32

57

1.39 (0.77–2.50)

0.275

1.35 (0.75–2.44)

0.321

C3

0.259

 P50 < 1313.00

51

115

1.00

–

1.00

 P50 - P75 (1313.00–1457.00)

30

59

1.18 (0.65–2.12)

0.592

1.15 (0.63–2.08)

0.650

 P75 > 1457.00

34

56

1.37 (0.76–2.46)

0.296

1.33 (0.74–2.41)

0.342

C4

0.336

 P50 < 252.50

51

115

1.00

–

1.00

–

 P50 - P75 (252.50–305.25)

31

58

1.20 (0.69–2.08)

0.514

1.18 (0.68–2.05)

0.558

 P75 > 305.25

33

58

1.33 (0.74–2.39)

0.349

1.25 (0.69–2.29)

0.463

ferritin

0.943

 P50 < 39.3550

59

115

1.00

–

1.00

–

 P50 - P75 (39.3550–82.7550)

26

59

0.83 (0.45–1.54)

0.558

0.81 (0.44–1.53)

0.522

 P75 > 82.7550

30

57

1.02 (0.56–1.86)

0.949

1.03 (0.56–1.88)

0.922