Table 1 Summary of findings for medications to prevent preeclampsia

Antiplatelets + calcium (1 RCT; 334 participants)

0.16 (0.03 to 0.75)

⊕⊕⊝⊝

Low^a,b

0.45 (0.05 to 4.06)

⊕⊕⊕⊝

Moderate^b

0.19 (0.04 to 0.86)

[0.04 to 1.01]

⊕⊕⊝⊝

Low^a,b

89.9%

There was no evidence of inconsistency for global inconsistency test (P = 0.459) and Dias’s inconsistency tests of the node splitting

Anticoagulants + antiplatelets + calcium (2 RCTs; 156 participants)

0.24 (0.03 to 1.79)

⊕⊝⊝⊝

Very low^c,d

0.24 (0.03 to 1.79)

[0.03 to 2.07]

⊕⊝⊝⊝

Very low^c,d

78.3%

Anticoagulants + antiplatelets (1 RCT; 20 participants)

0.31 (0.07 to 1.27)

⊕⊝⊝⊝

Very low^d,e

0.46 (0.26 to 0.80)

⊕⊕⊝⊝

Low^d

0.43 (0.26 to 0.73)

[0.19 to 1.01]

⊕⊕⊝⊝

Low^d

74.2%

Calcium + antioxidants (1 RCT; 660 participants)

0.39 (0.16 to 0.96)

⊕⊕⊝⊝

Low^e

0.93 (0.18 to 4.82)

⊕⊕⊕⊝

Moderate^b

0.47 (0.20 to 1.06)

[0.16 to 1.35]

⊕⊕⊕⊝

Moderate^b

66.8%

Calcium (13 RCTs; 26,021 participants)

0.61 (0.46 to 0.80)

⊕⊕⊕⊝

Moderate^f

0.69 (0.20 to 2.36)

⊕⊕⊕⊝

Moderate^b

0.61 (0.47 to 0.80)

[0.30 to 1.24]

⊕⊕⊕⊝

Moderate^f

54.4%

Anticoagulants (2 RCTs; 399 participants)

0.70 (0.28 to 1.79)

⊕⊕⊕⊝

Moderate^b

0.23 (0.02 to 2.28)

⊕⊕⊕⊝

Moderate^b

0.60 (0.25 to 1.43)

[0.20 to 1.80]

⊕⊕⊕⊝

Moderate^b

51.7%

Antiplatelets (31 RCTs; 41,953 participants)

0.68 (0.57 to 0.82)

⊕⊕⊝⊝

Low^a,f

0.79 (0.27 to 2.33)

⊕⊕⊕⊝

Moderate^b

0.69 (0.57 to 0.82)

[0.35 to 1.35]

⊕⊕⊕⊝

moderate^f

43.7%

Antiplatelets + nitric oxide (No direct comparison)

0.80 (0.31 to 2.05)

[0.25 to 2.55]

⊕⊕⊝⊝

low^d

34.5%

Antioxidants (25 RCTs; 24,768 participants)

0.76 (0.63 to 0.92)

⊕⊕⊕⊝

Moderate^f

2.72 (0.27 to 27.33)

⊕⊕⊕⊝

Moderate^b

0.77 (0.63 to 0.93)

[0.39 to 1.52]

⊕⊕⊕⊝

Moderate^f

32.3%

Nitric oxide (1 RCT; 68 participants)

1.35 (0.61 to 3.01)

⊕⊝⊝⊝

Very low^d,e

1.35 (0.49 to 3.77)

[0.39 to 4.65]

⊕⊝⊝⊝

Very low^d,e

11.4%