Comparison 1. Nitric oxide donors versus placebo or no treatment.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Prolongation of pregnancy greater than 48 hours	2	186	Risk Ratio (M‐H, Random, 95% CI)	1.19 [0.74, 1.90]
2 Birth prior to 37 completed weeks	2		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
3 Birth prior to 34 completed weeks	1	153	Risk Ratio (M‐H, Fixed, 95% CI)	0.93 [0.61, 1.41]
4 Birth prior to 28 completed weeks	1	153	Risk Ratio (M‐H, Fixed, 95% CI)	0.50 [0.23, 1.09]
5 Caesarean section	1	33	Risk Ratio (M‐H, Fixed, 95% CI)	0.47 [0.14, 1.57]
6 Any adverse drug reactions	2	186	Risk Ratio (M‐H, Fixed, 95% CI)	1.49 [1.14, 1.94]
7 Headache	1	153	Risk Ratio (M‐H, Fixed, 95% CI)	1.95 [1.31, 2.90]
8 Dizziness	1	153	Risk Ratio (M‐H, Fixed, 95% CI)	1.60 [0.60, 4.28]
9 Flushing	1	153	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.43, 1.89]
10 Hypotension	1	153	Risk Ratio (M‐H, Fixed, 95% CI)	1.20 [0.49, 2.95]
11 Completion of course of maternal steroids	2	186	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.90, 1.20]
12 Death unrelated to congenital abnormalities	2		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
12.1 In utero	1	153	Risk Ratio (M‐H, Fixed, 95% CI)	0.36 [0.01, 8.59]
12.2 In first 28 days of life	2	186	Risk Ratio (M‐H, Fixed, 95% CI)	0.43 [0.06, 2.89]
12.3 After 28 days	0	0	Risk Ratio (M‐H, Fixed, 95% CI)	0.0 [0.0, 0.0]
13 Intraventricular haemorrhage	1	153	Risk Ratio (M‐H, Fixed, 95% CI)	2.14 [0.20, 23.06]
14 Respiratory distress syndrome	1	33	Risk Ratio (M‐H, Fixed, 95% CI)	0.47 [0.14, 1.57]
15 Chronic lung disease	1	153	Risk Ratio (M‐H, Fixed, 95% CI)	0.15 [0.02, 1.21]
16 Birthweight (grams)	1	33	Mean Difference (IV, Fixed, 95% CI)	327.0 [‐272.13, 926.13]
17 (Non‐prespecified) Composite outcome: serious infant morbidity or mortality	1	153	Risk Ratio (M‐H, Fixed, 95% CI)	0.29 [0.08, 1.00]