Nine RCTs were included, with clinicians and patients blinded to group assignment (total n=957).
Endometritis: there was a non significant trend towards the reduction of endometritis (pooled random-effects OR 0.61, 95% confidence interval, CI: 0.34, 1.08; based on 6 studies).
Chorioamnionitis: antibiotic therapy was protective against chorioamnionitis (pooled random-effects OR 0.54, 95% CI: 0.31, 0.95; based on 6 studies). Antibiotic therapy was therefore protective against in utero infection.
Perinatal mortality: a reduction in perinatal mortality was found with fixed-effect meta-analysis (summary OR 0.50, 95% CI: 0.29, 0.85) and random-effects meta-analysis (summary OR 0.50, 95% CI: 0.26, 0.97). Antibiotic therapy therefore reduces the risk of perinatal death.
Respiratory distress syndrome (7 studies): no significant effect (fixed-effect summary OR 0.89, 95% CI: 0.65, 1.24; random-effects OR 0.89, 95% CI: 0.64, 1.25) was observed.
Necrotising enterocolitis: no significant effect (fixed-effect summary OR 1.06, 95% CI: 0.60, 1.88; random-effects OR 1.06, 95% CI: 0.640, 1.88) was observed.
Latency periods greater than 48 hours (4 studies): antibiotic therapy increased the likelihood of a latency period greater than 48 hours in the fixed-effect model (summary OR 2.18, 95% CI: 1.25, 3.80) but not the random-effects model (summary OR 1.50, 95% CI: 0.86, 2.64).
Latency periods greterh than 168 hours (4 studies): antibiotic therapy increased the likelihood of a latency period greater than 168 hours in both the fixed-effect model (summary OR 3.53, 95% CI: 2.13, 5.85) and the random-effects model (summary OR 3.54, 95% CI: 2.12, 5.89).
Neonatal sepsis (6 studies): no significant reduction although a trend towards reduction in risk of sepsis was found (fixed-effect summary OR 0.69, 95% CI: 0.38, 1.26; random-effects OR 0.65, 95% CI: 0.33, 1.28).
Survival: 4 studies examined survival and found significant advantages for the antibiotic group in terms of survival. One study showed a significant difference in birth weight between the two groups. Two studies showed significant increases in the length of the latency period within the treatment groups.