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Table 2 A summary of effect size for tocolytic treatment versus placebo for extremely preterm birth outcomes in RCTs

From: Tocolysis for inhibiting preterm birth in extremely preterm birth, multiple gestations and in growth-restricted fetuses: a systematic review and meta-analysis

Tocolysis compared to placebo in women with extremely preterm birth (RCTs)
Patient or population: Women with extremely preterm birth
Intervention: Tocolysis (atosiban and ritodrine)
Comparison: Placebo
Outcomes Anticipated absolute effectsf (95 % CI) Relative effect (95 % CI) № of participants (studies) Quality of the evidence (GRADE)
Risk with placebo Risk with tocolysis
Prolongation of pregnancy >24 h Study population RR 1.15 (0.81 to 1.63) 77 (1 RCT) MODERATE a
59 per 100 68 per 100 (476 to 959)
Prolongation of pregnancy >48 h Study population RR 1.40 (0.83 to 1.31) 117 (2 RCTs) VERY LOW a,b
69 per 100 96 per 100 (57 to 90)
Prolongation of pregnancy >7 days Study population RR 1.05 (0.75 to 1.48) 117 (2 RCTs) VERY LOW a,b
65 per 100 68 per 100 (49 to 96)
Perinatal death Study population RR 2.22 (0.26 to 19.24) 265 (2 RCTs) VERY LOW c,d,e
17 per 100 37 per 100 (4 to 100)
GRADE Working Group grades of evidence
High quality: We are very confident that the true effect lies close to that of the estimate of the effect
Moderate quality: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different
Low quality: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect
Very low quality: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect
aTotal number of cases less than 300
bAllocation concealment not performed
cOne study with unclear randomization and one study without allocation concealment
dLarge heterogeneity (>60 %)
eSmall sample size (<300) and wide confidence interval
  1. CI Confidence interval; RR Risk ratio; OR Odds ratio
  2. fThe risk in the intervention group (and its 95 % confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95 % CI)